According to scholars David Hatch and Stephen Millward, Black Sabbath, and the numerous heavy metal bands that they inspired, have concentrated lyrically "on dark and depressing subject matter to an extent hitherto unprecedented in any form of pop music".
Segundo os investigadores David Hatch e Stephen Millward, Black Sabbath e os numerosos grupos de heavy metal que estes inspiraron, concentráronse en líricas "de contido escuro e depresivo ata unha extensión ata o de agora sen precedentes en ningunha forma de música popular".