there must be thousands, and in my hardrive alone, but to pick, well since I'm a little pressed for time right now, if you're in to Gothic Metal, definitely most if not all by Sirenia and Tristania, more specifically right off the top of my head
Tristania-Beyond The Veil, Angina
Sirenia-At Sixes and Sevens, On The Wane, Euphoria
but hell even in power metal you'll find them, just earlier I was listening to 'prophet of the last eclipse' from luca turilli and was amazed at the choir work on that song, which is btw, now my favorite song from them..just thought I'd throw that in there...but for now I must leave...oh and and...there's 'Voyage Of Gurdjieff (The Fourth Way)' and 'lemuria' from therion but...
/end

Oh how convenient. A theory about God that doesn't require looking through a telescope.