No one will like the music I suggest, but i'll post It anyways.
Thrash:
Megadeth, because Dave is the guy who invented the hard stuff in metal
Pantera, because of Dimebags great riffs
Sepultura, because they inspired the early death metal bands
Melodeath:
Soilwork, because they have awsome melodies.
Mors Principium Est, because of their melodic and technical skills
Arch Enemy, because of great guitars and vocals
In Flames (Only pre-Clayman), because of the melodies.
Children of Bodom, because the guitars are simply amazing.
Death metal:
Cannibal Corpse, because of the brutality
Necrophagist because of awesome melody, technique and brutality.
Black metal:
Immortal, because of great lyrics
Satyricon, because they rock
Enslaved, because of the musical feeling
Finntroll, because of trolls and folk music influences
Punk/Hardcore/Grind:
Cheap sex, because of great lyrics (especially "Fuck emo")
Napalm Death, because they're awsome
Bad religion, because they are a decent punk band and not some emo posers