A light metal is any metal of relatively low density. More specific definitions have been proposed; none have obtained widespread acceptance. Magnesium, aluminium and titanium are light metals of significant commercial importance. Their densities of 1.7, 2.7 and 4.5 g/cm3 range from 19 to 56% of the densities of the older structural metals,iron (7.9) and copper (8.9).
Most of light metals are less toxic than heavy metals.Beryllium is toxic but it is rare.Vanadium that sometimes look as light metal is toxic.Other light metals be toxic when a big dose.