Elements or mixtures of elements (see 'Alloy') that possess high electrical conductivity and a lustrous appearance in the solid state. Metals are usually divided into two groups: ferrous (steel and iron) and non-ferrous. The non-ferrous metals can be subdivided into the noble or precious metals, e.g. gold, silver, and the platinum group, and the base metals, e.g. copper, lead, mercury, nickel, tin, zinc. The noble metals do not corrode nearly as rapidly as the base metals.