Not one of my favorite bands, but one of my favorite songs -- A 10-minute-long, near perfect blend of metal, orchestra, choir, and quasi-operatic vocals. I'm not a huge fan of metal music generally, but since I have a soft spot for anything orchestral I quickly fell for this. They have quite a few other songs backed with orchestra and choir, and they're done quite well.
Unfortunately I couldn't find any performances actually featuring the choir and orchestra -- in this video the band is performing along with pre-recorded orchestra and choral tracks.
I don't follow this band very closely, but I do know that the singer featured in this video has been replaced, which caused quite a stir among fans. I have two of their albums that feature the singer in this video, and really enjoy the more orchestral tracks on them.