Definitions of heavy metal
a metal of relatively high density (specific gravity greater than about 5) or of high relative atomic weight (especially one that is poisonous like mercury or lead)
a mixture containing two or more metallic elements or metallic and nonmetallic elements usually fused together or dissolving into each other when molten
metal, metallic element
any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.
loud and harsh sounding rock music with a strong beat; lyrics usually involve violent or fantastic imagery