I kept quiet when Petra was picked, because I didn't want to tip my hand as to this next pick:
Stryper - To Hell With the Devil (1986)
To Hell with the Devil is the
Grammy Award nominated fourth release, and third full-length album, by the
Christian metal and
Glam metal band
Stryper, released in 1986 (see
1986 in music).
[1] It was both the first
Contemporary Christian and
Christian metal album to achieve
Platinum status, selling over one million copies. It remains the best-selling Christian metal album of all time.
The album was listed at #88 in the 2001 book,
CCM Presents: The 100 Greatest Albums in Christian Music. The album was the only Heavy Metal album on the list.
Ian Christe, author of the heavy metal history book
Sound of the Beast: The Complete Headbanging History of Heavy Metal (2003), mentions
To Hell with the Devil in his book as one of the landmarks of the
glam metal movement.
[2]
Personally, I don't think this counts as heavy metal, but the music is pretty good.