Metals

Metals are a broad class of elements known for high electrical and thermal conductivity, malleability, ductility, and a characteristic metallic luster. They are typically solid with high densities and melting points, though exceptions exist, such as mercury, which is liquid at room temperature. Metals form positive ions and are held together by metallic bonds, which give them their distinctive ability to conduct heat and electricity and to be shaped without breaking.

Metals occur in the Earth's crust mainly as minerals called ores. Extraction generally involves mining, followed by processing that may include smelting to reduce oxides or, for some metals like aluminum, electrolysis. They are commonly categorized as ferrous metals, which contain iron, and non-ferrous metals, which do not. Examples of metals include iron, copper, aluminum, zinc, lead, tin, nickel, titanium, and the noble metals such as gold and platinum.

Alloys are materials produced by combining two or more elements, at least one of which is a metal, to achieve improved properties. Common alloys include steel (iron and carbon), stainless steel (iron with chromium and other elements), bronze (copper and tin), and brass (copper and zinc). Alloys often offer enhanced strength, hardness, or corrosion resistance compared with their constituent elements.

Metals have wide-ranging applications in construction, transportation, electronics, machinery, and consumer goods. They are also used as catalysts and in specialized technologies such as magnets and superconductors. Choices among metals depend on factors like strength, weight, ductility, corrosion resistance, and cost.

Environmental and social considerations include mining impacts, energy use in refining, and the toxicity of certain metals. Recycling is common and beneficial, reducing energy requirements and conserving resources.