After our religion classes had to listen to recordings of the christian rock songs now in heavy rotation during school masses, some of my friends and I began joking about our school starting to include christian hardcore songs in the mass repertoire. Christian hardcore, for those normal enough to classify modern music into simple rock and rap genres, is a heavy metal offshoot, that derives its musical sound from death metal, but rather than satanic and secular lyrical themes, it uses the New Testament for lyrical muse.
It was only a matter of time before various heavy metal sub-genres started adopting christian themes because modern metal is usually associated with dramatic lyrical themes. Some kids that grew up listening to traditional metal bands liked the sound, but rejected the whole satanic image because of their christian upbringings. When they started their own bands, they used the traditionally brutal sound and delivery of the music to depict gospel images and themes. These bands are used as a form of ministry, intending to bring God into the lives of angry kids.