Honestly Metal would just kill the feel of space combat for me. 
Anything with vocals is just horrible space battle music if you're involved with it. Watching one isn't all that bad, especially when they use a choir like Immediate Music tracks do.
Bang Camaro, FTW.

I listen to them while I play Halo 3, and it works quite well.

Not the heaviest rock like Judas Priest, but I like it plenty.
I agree with your notion of vocals making bad battle music, but Bang Camaro uses a 20-man choir that I think blends in quite well to the background.
Some kickass guitar solos too, IMHO.
