If I'm painting at GW, I won't listen to anything. I prefer chatting with the other people around the table and in the store. If I'm at home, however, it's generally just whatever my ipod throws up on shuffle. Mostly metal, some classic rock, punk or grunge.
Stuff that usually crops up includes Nightwish, Within Temptation, Manowar, Bad Religion, Alice in Chains and half of the usual 'classic rock' bands.