Check out old metal bands like STRYPER, SHOUT, WHITECROSS, Tamplin & Friends, Angelica etc
Stryper, Shout and Tamplin are really good. "In God We Trust" by Stryper is a good album.
For me PETRA is the best Christian band ever. They are not metal. But heavy rock. Lyrically and musically excellent.
On Fire, Beyond Belief, No Doubt, Unseen Power, Wake-up Call, The Rock cries out, Jekkyll & Hyde...are some of the best PETRA albums. The lyrics are straight from the scriptures.
Petra lead vocalist,John Schlitt has also released couple of good solo albums of which SWING is good.
Michael Sweet of Stryper has also gone single and did a good job. TAMPLIN was actually the lead vocalist of Shout. He is a crack pot.
I am also on the look out of good metal, heavy rock bands which stand loud and tall for Jesus.