I don't know if I'll be much help on this as I've only been playing a short while but I know Rammstein's song "Asche zu Asche" (on the Herzeleid album) has keyboards in it as well as a small and simple solo for it as well. The tab for it doesn't look to difficult but you'll need a singer and someone doing small backups on it as well.

Rammstein is the only metal type band I can think of that basically has what you require. Hope this helps :)

EDIT: You may get out of singing it if you don't know german, I once looked for an english version of the lyrics and couldn't find one. :(