Porcupine Tree
Opeth
Fates Warning
You could check out some doom bands like Swallow the Sun or My Dying Bride.
Listen to classic rock like the Scorpions, Neil Young, Jethro Tull, Styx, etc.
Deadboy And The Elephantmen
Katatonia
Arcturus
Orange Goblin
Radiohead
Agalloch
Porcupine Tree
Age Of Silence
Amorphis
Turisas
Jimi Hendrix
Tool/APC
Ulver
Anathema
Pearl Jam
Antimatter
Riverside
Frank Sinatra
Placebo
Circa Survive
Circus Maximus
Clutch
Devin Townsend
The Fratellis
Symphony X - Great Power Metal vocals by Russell Allen. Sure you've probably heard them though.
Genesis - Peter Gabriel era has ethereal vocals. Gotte respect Genesis.
Amorphis - Eledgy & onward has a lot of clean/harsh mixed vocals for good contrast, but the clean vox are great.
Devin Townsend - Great range of style & development.
Yngwie Malmsteen - Always got some of the greatest vocalists IMO. Start with his early stuff, which is mostly all good. As he progressed he got hit or miss, but mostly miss
Porcupine Tree
Devin Townsend
Katatonia
The Foreshadowing
Ihsahn - The Adversary (mixed clean and blackmetal vocals)
Thurisaz - Circadian rhythm (" " " ")
Amorphis
Riverside
Oblique Rain
Anathema - Judgement and Alternative 4
All 5 albums in my sig