Themes of lyricism
Black Sabbath and the numerous heavy metal bands that they inspired, according to David Hatch and Stephen Millward, have focused lyrically "on gloomy and depressing subject matter to a level historically unseen in any form of pop music." They use Sabbath's second album, Paranoid (1970), as an example "Songs dealing with personal trauma, such as'Paranoid'and'Fairies Wear Boots'(which described the unpleasant side effects of drug use), as well as those dealing with larger issues, such as the self-explanatory ‘War Pigs'and'Hand of Doom ', were included.
Sex is another major issue that runs from Led Zeppelin's suggestive lyrics to the more explicit references of glam metal and nu metal bands, owing to the genre's roots in blues music.
King Diamond is recognized for producing horror-themed conceptual lyrics. Heavy metal's thematic material has long been a source of controversy. Jon Pareles claims that "The basic subject matter of heavy metal is straightforward and almost universal. It celebrates... a party without limits... with grunts, moans, and subliterary lyrics... The core of the music is styled and formulaic..." Metal lyrics have been judged immature and uninteresting by some music critics, while others have complained to what they see as misogyny and occult propaganda by others.
The Parents Music Resource Center petitioned the United States Congress in the 1980s to control the popular music industry because of what it claimed were unpleasant lyrics, notably in heavy metal songs.