Check out older Theatre Of Tragedy, back when they actually played metal. Not that I dislike their electronica stuff, she just isn't with the band now.
FYI Tarja is ex-Nightwish, but still in my opinion the best female metal artist. Followed by Vibeke Stene (ex Tristania). Amy Lee is good, but doesnt even come close to Tarja, Vibeke, or even Anette Olzon for that matter