A metal with a specific gravity greater than about 5.0, especially one that is poisonous, such as lead or mercury.
effects are:-
Living organisms require trace amounts of some heavy metals, including iron, cobalt, copper, manganese, molybdenum, vanadium, strontium, and zinc, but excessive levels can be detrimental to the organism. Other heavy…[Read more]

Probably because they have good chemistry when they act in movies…