Metals are made of atoms of metallic elements, held together by a unique type of chemical bond. Unlike most materials, metal atoms share their outermost electrons freely with all their neighbors, creating what chemists call a “sea of electrons” that flows around a grid of positively charged atoms. This structure is what gives metals their signature properties: they conduct electricity, they’re strong, and they can be bent without breaking.
About 90 of the 118 known elements on the periodic table are metals. Some metals you encounter daily, like iron or aluminum, are single elements mixed with small amounts of other elements. Others, like steel or bronze, are deliberate mixtures called alloys. Understanding what metals are made of starts at the atomic level and builds up to the materials you actually use.
How Metal Atoms Bond Together
The defining feature of any metal is how its atoms connect. Each metal atom releases one or more of its outer electrons, which don’t stay attached to any single atom. Instead, these electrons become “delocalized,” meaning they drift freely throughout the entire structure. Picture a lattice of positively charged metal ions sitting in a shared pool of negative electrons. The attraction between the positive ions and this electron cloud is what holds the whole structure together.
This is fundamentally different from how other materials work. In salt, positive and negative ions lock into fixed pairs. In water, atoms share electrons in tight bonds between specific partners. In metal, the sharing is communal. Iron atoms, for instance, each give up one or more electrons to the collective pool, becoming positively charged ions (Fe⁺). Those ions are then attracted to the surrounding electron sea, which keeps the entire metal lattice locked in place. This bonding style explains why metals conduct electricity so well: those free-roaming electrons can carry an electric current with very little resistance.
What Determines a Metal’s Properties
All metals share the same basic bonding structure, but the specific element determines how that structure behaves. The number of protons in the nucleus defines which element it is, and the number of electrons each atom contributes to the shared pool affects strength, conductivity, and melting point.
Conductivity varies significantly. Silver has the highest electrical conductivity of any metal. On a relative scale of 0 to 100, silver scores 100, copper comes in at 97, and gold sits at 76. That’s why copper wiring is standard in homes: it’s nearly as conductive as silver at a fraction of the cost.
Melting points span an enormous range. Mercury melts at -39°C, which is why it’s liquid at room temperature. Tungsten, at the other extreme, doesn’t melt until 3,422°C, making it ideal for light bulb filaments and cutting tools. This 3,400-degree range exists because different metal atoms pack together with varying tightness and bond strength.
The Main Categories of Metals
The periodic table organizes metals into groups based on their atomic structure and behavior. Alkali metals (like sodium and potassium) sit in the first column and each give up one electron easily. Alkaline earth metals (like calcium and magnesium) are in the second column and give up two. Transition metals, the large block in the middle that includes iron, copper, gold, and titanium, can give up varying numbers of electrons, which is why they form such a wide variety of compounds and alloys.
A more practical way to classify metals splits them into ferrous and non-ferrous. Ferrous metals contain iron. They’re known for high tensile strength, which is why they’re used in skyscrapers, bridges, and railways. Most ferrous metals are magnetic and prone to rust, with two notable exceptions: stainless steel resists rust because of added chromium, and wrought iron resists it due to its high pure-iron content. Non-ferrous metals, like aluminum, copper, and titanium, contain no iron. They’re lighter, more resistant to corrosion, and not magnetic, making them essential in aerospace and electronics.
Pure Metals vs. Alloys
Very few metals are used in their pure elemental form. Most of the metal objects around you are alloys, which are mixtures of two or more elements designed to improve on what any single metal can do alone. Steel is iron combined with a small percentage of carbon. Bronze is copper mixed with tin. Brass is copper mixed with zinc. In each case, adding another element changes how the atoms pack together, which alters strength, flexibility, or corrosion resistance.
Modern engineering takes this much further. Nickel-based superalloys used in jet engines contain additions of cobalt, tungsten, molybdenum, and other elements that help them survive extreme heat without warping. Even tiny additions matter: adding just 0.5% titanium to certain nickel alloys significantly improves their ability to resist deformation at high temperatures. The strongest permanent magnets in the world are made from neodymium, iron, and boron melted together and cast into solid form. These neodymium magnets power everything from electric vehicles to wind turbines.
Where Metals Come From in Nature
A handful of metals, notably gold and platinum, occur in nature as pure elements. You can find gold nuggets because gold is so chemically stable that it doesn’t readily bond with other elements. Most metals, though, are locked inside chemical compounds in rock formations called ores. Iron is typically bound to oxygen in iron oxide. Copper and silver are often bonded to sulfur, forming sulfide minerals. In the silver mines of Virginia City, Nevada, for example, silver was most commonly found as silver sulfide (Ag₂S).
Extracting a usable metal from ore requires breaking these chemical bonds, usually through heating with a reducing agent or passing electricity through a molten compound. The process strips away the oxygen, sulfur, or other elements and leaves behind the pure metal, which can then be refined and alloyed for specific uses. Aluminum, the most abundant metal in Earth’s crust, requires enormous amounts of electricity to extract from its ore, which is why aluminum recycling saves up to 95% of the energy needed to produce it from scratch.
Why Metal Behaves the Way It Does
Every property you associate with metal traces back to that shared electron cloud. Metals conduct heat and electricity because free electrons carry energy quickly through the structure. Metals are shiny because those electrons absorb and re-emit light at the surface. Metals can be hammered into sheets or drawn into wire because the ions can slide past each other without breaking the bond. The electron sea simply rearranges around the ions in their new positions.
This is also why metals feel cold to the touch. They aren’t actually colder than the room around them, but they conduct heat away from your skin so efficiently that your nerves register a rapid temperature drop. Wood and plastic, which lack free-moving electrons, insulate instead of conduct, so they feel warmer even at the same temperature. The material itself hasn’t changed. What changed is how fast it pulls heat from your hand.