Oh boy, where do I even begin? There are so many bands out there... These are in no particular order of which is better or anything like that, and I don't really bother with keeping up with subgenre labels anymore, so it's a bit of a jumbled together mashup of different genres:
Metallica (although I prefer their older material, pre-Black Album)
Megadeth
Kreator
Sodom
Slayer
Motorhead
Judas Priest
Metal Church
Quo Vadis
Cynic
Beyond Creation
Rivers of Nihil
Septicflesh
Godflesh Apocalypse
Amon Amarth (probably one of my absolute favorite metal bands of all time)
Testament
Enslaved
Electric Wizard
Sleep
High on Fire
Nevermore
Sanctuary
The Obsessed
St. Vitus
Pagan Alter
Witchcraft
Venom
Carcass
Hypocrisy
Pantera
Tyr
Celtic Frost
Toxic Holocaust
Midnight
Type O-Negative
Candlemass
Death
Devin Townsend Project
Strapping Young Lad
Dio
Soilwork
In Flames
King Diamond
Mercyful Fate
Sabaton
Orchid
Eluveitie
Ensiferum
Turisas
Finntroll
Municipal Waste
Iron Reagan
Iron Maiden
Cattle Decapitation
Obituary
Cannibal Corpse
Suffocation
Accept
Power Trip
Ihsahn
Exmortus
Dark Tranquility
Black Label Society
Angel Witch
Black Sabbath
This is by no means the end all, be all of my list of favorite bands. These are just the ones I could remember off the top of my head (and maybe with a little help from my Spotify list, but we'll just keep that between us ).
Regarding Amon Amarth, they are currently on tour in the US right now, and last weekend they played at the Fillmore in Charlotte, NC. That was one hell of a show they put on. The openers for them were really good too. If y'all ever get a chance to go see AA live, do it. You won't regret it. You guys been to any shows recently?