Definition of "heavy metal"

(sciences, countable) Any metal that has a specific gravity greater than about 5, especially one, such as lead, that is poisonous and may be a hazard in the environment. (There are many different definitions of what counts as a heavy metal; see Heavy metals for a discussion.)  examples

(music, uncountable) A genre descended from rock music, characterized by massive sound, highly amplified distortion, and overall loudness, often with extended guitar solos, and lyrics that involve aggressive or fantastic imagery.  examples

(uncountable) guns or shot of large size.  examples

(uncountable, figurative) Great influence or power.  examples