From Longman Dictionary of Contemporary Englishheavy metalˌheavy ˈmetal noun 1 APM[uncountable] a type of rock music with a strong beat, played very loudly on electric guitars2 [countable] technicalT a metal that has a high density, such as gold, mercury, or lead. Many heavy metals are poisonous.
Examples from the Corpus
heavy metal• A heavy metal vision of post-Thatcherism, maybe.• Into most music except heavy metal, house, jazz and soul!• Daeve Pope would have been in heavy metal heaven.• I think there are a lot of gay people in heavy metal -- everywhere.• Secondly, the band launched heavy metal hard man Ted Nugent, one of rock's more notable characters.• The most successful title of this type is the heavy metal bible, Kerrang. 