The term ‘metal’ is derived from the Greek word ‘metallon,’ which means ‘to extract’ or mine from the ground. Our planet contains plenty of metal. In fact, out of 118 elements in the periodic table, about 95 are metal.
The number isn’t exact because the boundary between metals and nonmetals is quite vague: there is no standard definition of a metalloid, nor is there any complete agreement on the elements appropriately classified as such.
While the history of refined material begins with the use of copper 11,000 years ago, several subsequent developments and advances in manufacturing processes gave rise to the industrial revolution.
Today, we use different types of metals without even noticing them. From the clamps in your plumbing to the device you are using to read this article, all are made of certain metals. In fact, some metal elements are necessary for biological functions like oxygen flow and transmission of nerve impulses. Some are also commonly used in medicine in the form of antacids.
All metals in the periodic table can be categorized according to their chemical or physical properties. Below, we have listed some different types of metals along with their real-world applications.
Classification By Physical Properties
14. Light Metals
Titanium 6AL-4V alloy
Examples: Aluminum, titanium, magnesium
Light metals have relatively low density. There is no formal definition or criteria to identify these metals, but hard elements with densities lower than 5 g/cm3 are generally considered as light metals.
Light-metal metallurgy was first developed in the mid-19th century. While most of them occur naturally, a significant amount is produced via electrothermy and electrolysis of fused salts.
Their alloys are extensively used in the aircraft industry due to their low density and sufficient mechanical properties. Titanium 6AL-4V alloy, for example, accounts for almost 50 percent of all alloys used in aircraft applications. It is used to build rotors, compressors blades, nacelles, and hydraulic system components.
13. Heavy Metals
Oxidized lead nodules and 1 cm3 cube
Examples: Iron, copper, cobalt, gallium, tin, gold, platinum
Heavy metals are elements with relatively high densities (usually over 5 g/cm3) and atomic weights. They tend to be less reactive and have far fewer soluble sulfides and hydroxides than lighter metals.
These metals are rare in the Earth’s crust, but they are present in various aspects of modern life. They are used in solar panels, cell phones, vehicles, antiseptic, and particle accelerators.
Heavy metals often get mixed in the environment due to industrial activities, degrading soil, water, and air quality, and subsequently causing health issues in animals and plants. Vehicle emissions, mining and industrial waste, fertilizers, lead-acid batteries, and microplastics floating in the oceans, are some of the most common sources of heavy metals in this context.
12. White Metal
White metal bearings
Examples: Generally made of tin, lead, bismuth, antimony, cadmium, zinc
White metals are various light-colored alloys used as a base for ornaments or silverware. Many tin-based or lead-based alloys, for example, are used in jewelry, bearing, fusible plugs, and miniature figures.
A white metal alloy is made by combining certain metals in fixed proportions, as per the final product’s requirement. The base metal for jewelry, for instance, is molded, cooled, extracted, and then polished to give a precise shape and shiny look.
They are also used for manufacturing general-purpose heavy bearings, medium-sized internal combustion bearings, and electrical machines.
11. Brittle Metal
Brittle fracture in cast iron
Examples: Alloys of carbon steel, cast iron, and tool steel
A metal is said to be brittle if it is hard but can’t resist an impact or load vibration. Such metals, when subjected to stress, break without notable plastic deformation. They have low tensile strength and often make a snapping sound when they are broken.
Many steel alloys become brittle at low temperatures, based on their processing and composition. Pig iron, for instance, is hard but brittle due to high carbon content. In contrast, ceramic and glass are much more brittle than metals because of their ionic bonds.
Gallium, bismuth, chromium, manganese, and beryllium are also brittle. They are often used in various civil and military applications involving high-strain-rate loadings. Cast iron, which is resistant to damage by oxidation, is used in machines, pipes, and automotive industry parts like gearbox cases and cylinder heads.
10. Refractory Metals
A microscopic image of the tungsten filament in an incandescent light bulb | Wikimedia
Examples: Molybdenum, tungsten, tantalum, rhenium, niobium
Refractory metals have extremely high melting points (over 2000 °C) and are resistant to wear, deformation, and corrosion. They are good conductors of heat and electricity and have high densities.
Another key characteristic is their thermal shock resistance: they do not easily expand or crack under repeated heating and cooling. However, they can deform under high-stress loads and oxidize at high temperatures.
Their strenght and hardness make them ideal for drilling and cutting tools. Refractory metal carbides and alloys are used in almost all industries, including mining, automotive, aerospace, chemical, and nuclear technology.
9. Ferrous and Non-Ferrous Metals
Gear shafts made of (ferrous) stainless steel
Ferrous Metals: Steel, pig iron, alloys of iron
Non-Ferrous Metals: Copper, aluminum, lead, zinc, silver, gold
The term ‘ferrous’ comes from the Latin word ‘Ferrum,’ which translates to ‘iron.’ Thus, ferrous means generally ‘containing iron,’ while non-ferrous describes metals and alloys that do not contain a sufficient amount of iron.
Since ferrous materials can have a wide range of alloying elements that greatly change their characteristics, it is very difficult to place the properties of all ferrous metals under one umbrella. However, some generalization can be made, such as most ferrous metals are hard and magnetic.
Ferrous metals are used for high load and low-speed applications, whereas non-ferrous metals are preferred for high speed and zero-load to low-load applications.
Steel is the most common ferrous metal. It accounts for about 80% of all metallic material due to its availability, high strength, low cost, ease of fabrication, and a broad range of properties. It is widely used in construction and manufacturing industries. In fact, the growth in the production of steel shows the overall development of the industrial world.
8. Base and Noble Metals
An assortment of the noble metals | Wikimedia
Base Metals: Copper, aluminum, tin, nickel, zinc
Noble Metals: Rhodium, mercury, silver, ruthenium, osmium, iridium
Base metals are common and inexpensive metals that corrode, oxidize, or tarnish faster than other metals when exposed to air or moisture. They are abundant in nature and easy to mine.
They are widely used in industrial and commercial applications, and are invaluable to the global economy due to their utility and ubiquity. Some base metals have distinctive characteristics that cannot be duplicated by other metals. Zinc, for example, is used for galvanizing steel to protect it against corrosion, and nickel is used for making stainless steel.
Noble metals, on the other hand, are resistant to oxidation and corrosion in moist air. As per the atomic physics, noble metals have a filled electron d-band. According to this strict definition, copper, silver, and gold are noble metals.
They have applications in areas like ornamentation, metallurgy, and high technology. Their exact uses vary from one element to another. Some noble metals, such as rhodium, are used as catalysts in the chemical and automotive industries.
7. Precious Metals
Rhodium: 1 gram powder, 1 gram pressed cylinder, and 1 g argon arc remelted pellet | Image source: Wikimedia
Examples: Palladium, gold, platinum, silver, rhodium
Precious metals are considered to be rare and have high economic value. Chemically, they are less reactive than most elements (including noble metals). They are also ductile and have a high luster.
Several centuries ago, these metals were used as currency. But now, they are mostly regarded as industrial commodities and investment. Many investors buy precious metals (mostly gold) to diversify their portfolios or beat inflation.
Silver is the second most popular precious metal for jewelry (after gold). However, its importance extends well beyond beauty. It has exceptionally high thermal and electrical conductivity and extremely low contact resistance. This is why sliver is widely used in electronics, batteries, and antimicrobial agents.
Classification By Chemical Properties
6. Alkali Metals
Solid sodium metal
Examples: Sodium, potassium, rubidium, lithium, cesium, and francium.
Alkali refers to the basic nature of their metal hydroxides. When these metals react with water, they form strong bases that easily neutralize acids.
They are so reactive that they are usually found in nature merged with other substances. Carnallite (a potassium-magnesium chloride) and sylvite (potassium chloride), for example, are soluble in water and thus easily extracted and purified. Water-insoluble alkalis, such as lithium fluoride, also exist in Earth’s crust.
One of the most popular applications of alkali metals is the use of cesium and rubidium in atomic clocks, the most accurate time and frequency standards known. Lithium is used as an anode in lithium batteries, potassium composites are used as fertilizers, and rubidium ions are used in purple fireworks. Pure sodium metal is widely used in sodium-vapor lamps that produce light very efficiently.
5. Alkaline Earth Metals
Emerald crystal, the principal mineral of beryllium
Examples: Beryllium, calcium, magnesium, barium, strontium, and radium.
Alkaline earth metals are soft and silvery-white under standard conditions. They have low densities, boiling points, and melting points. While they are not as reactive as the alkali metals, they form bonds with elements very easily. Typically, they react with the halogens to form the alkaline earth metal halides.
They all occur in the Earth’s crust, except radium, which is a radioactive element. Radium has already decayed in the Earth’s early history due to its relatively short half-life (1600 years). Present-day samples come from the decay chain of uranium and thorium.
Alkaline earth metals have a wide range of applications. Beryllium, for instance, is used in semiconductors, heat conductors, electrical insulters, and military applications. Magnesium is often alloyed with zinc or aluminum to produce materials with specific properties. Calcium is mostly used as a reducing agent, and barium is used in vacuum tubes to remove gases.
4. Transition Metals
Examples: Titanium, vanadium, chromium, nickel, silver, tungsten, platinum, cobalt
Most elements use electrons from their outer shell to bond with other elements. Transition metals, however, can use two outermost shells to bond with other elements. It’s a chemical trait that enables them to bond with many different elements in various shapes.
They occupy the middle portion of the periodic table, serving as a bridge between (or transition) the two sides of the table. More specifically, there are 38 transition metals in groups 3 through 12 of the periodic table. They all are ductile, malleable, and good conductors of heat and electricity.
Many of these metals, such as copper, nickel, iron, and titanium, are used structurally and in electronics. Most of them form useful alloys with one another and with other metallic substances. Some of them, including gold, silver, and platinum, are called noble metals because they are highly unreactive and resilient towards acids.
3. Post-Transition Metals
Bismuth as synthetically made crystals | Wikimedia
Examples: Aluminum, gallium, tin, lead, thallium, indium, bismuth
The post-transition metals in the periodic table are elements located to the right of the transition metals and to the left of the metalloids. Due to their properties, they are also referred to as ‘poor’ or ‘other’ metals.
Physically, they are brittle (or soft) and have lower melting points and mechanical strength than transitions metals. Their crystalline structures are quite complex: they show covalent or direction bonding effects.
Different metals in this family have different uses. Aluminum, for instance, is used for making window frames, kitchen utensils, cans, foils, and vehicle parts. Tin alloys are used in soft solder, pewter, and superconducting magnets.
Indium is used to make flat-panel displays and touchscreen, and gallium has applications in fuel cells and semiconductors. Bismuth is used in Pepto-Bismol, a drug for treating stomach ulcers caused by a certain bacteria.
1-centimeter piece of pure lanthanum
Examples: Lanthanum, cerium, promethium, gadolinium, terbium, ytterbium, lutetium
Lanthanides are the rare earth metals with atomic numbers from 57 to 71. They were first discovered in 1787 in an unusual black mineral (Gadolinite) found in Ytterby, Sweden. The mineral was later separated into various lanthanide elements.
Lanthanides are highly dense metals with densities ranging from 6.1 to 9.8 g/cm3, and they tend to have very high boiling points (1200-3500 °C) and very high melting points (800-1600 °C).
Lanthanides alloys have been used for metallurgical applications due to their strong reducing abilities. About 15,000 tons of lanthanides are consumed every year as catalysts and in the production of glasses. They are also widely used in lasers and optical amplifiers.
Some studies show that lanthanides can be used as anticancer agents. Lanthanum and cerium, in particular, can inhibit the proliferation of cancer cells and promote cytotoxicity.
Uranium metal highly enriched in uranium-235 | Wikimedia
Examples: Actinium, uranium, thorium, plutonium, fermium, nobelium, lawrencium
Like lanthanides, actinides form a family of rare earth elements with similar properties. They are a series of 15 consecutive chemical elements in the periodic table from atomic numbers 89 to 103.
They all are radioactive in nature. Synthetically produced plutonium and naturally occurring uranium and thorium are the most abundant actinides on Earth. The first actinide to be discovered was uranium in 1789. And most of the existing actinides products were made in the 20th century.
Their properties, such as emission of radioactivity, pyrophoricity, toxicity, and nuclear criticality, make them hazardous to handle. Today, a significant portion of (short-lasting) actinides are made by particle accelerators for research purposes.
While some actinides have established daily-life applications, such as gas mantles (thorium) and smoke detectors (americium), most of them are used as a fuel in nuclear reactors and to make nuclear weapons. Uranium-235 is the most important isotope for nuclear power applications, which is widely used in thermal reactors.