metal

Definition

Chemical element that, in general, (1) is a good conductor of heat and electricity, (2) is opaque but good reflector of light when polished, (3) can be beaten into sheets, (4) can be drawn into wires, (5) produces a sonorous tone when struck. All metals crystallize under suitable conditions and (except cesium, gallium, and mercury) are solid at normal temperature. Chemically, metals tend to form positive ions (are electropositive) and most have strong reactive-affinity with certain non-metallic elements (such as chlorine and sulfur) with which they form salts. Trace quantities of some metals (such as cobalt, copper, iron, magnesium, potassium, sodium, and zinc) are essential to animal, human, and plant health.