I am really surprised that no one mentioned Geoff Tate from Queensryche. Technically he's one of the best in the metal scene, if not the best. But what makes him more than flawless screaming machine with endless breathe is that he can evoke feelings, through his voice. In addition to this, he is one of the very clever musician and talented lyric writer who could conceive a metal masterpiece, probably the best concept album, Operation: Mindcrime.
His voice can be full of anger, agony, desperation, excitement, love, revenge, thought, alienation... whatever the song requires. I REALLY recommend all of you, especially those who are interested in vocalists with both technique and emotion, to get those two albums:
1 - "Operation: Mindcrime": Probably the best concept album in metal and rock history. Not a single mediocre song, with clever story and great musicianship.
2 - "Promised Land": One of the most underapreciated and un-understood albums of rock history. A thematical album (not concept, because there's not an apparent story line, but every songs connect to each other and kinda forms an article) about life, life cycle, age, how the world changes, death, our existence.
I would avoid recommending single songs, as any song from both of the albums gets their full value when listened as a part of the album. They are both unique experiences, no rock or metal band/album has yet offered.
There was a project (I think called "Trinity") which would unite the talents of three best metal vocalists: Geoff Tate (Queensryche), Bruce Dickinson (Iron Maiden) and Rob Halford (Judas Priest). songs would be composed by Rob Z. According to his words, there would be special parts for each vocalist to song, according to the caracters of their voices and singing. it would be kinda like an opera. I'm very upset that it didn't continue.
@Albie: You must immediately order Bruce's "Chemical Wedding" !!! As it is a concept album, the kind bruce likes, and wanted to produces since Seventh Son record (which, in his opinion failed to be a concept album) He sings with so much enthusiasm, and his experience as a vocalist shows itself. Vocals on King in Crimson, Jerusalem, The Alchemist, Book Of Thel are so emotional, so strong... it's unforgettable.