Metallica
Megadeth
Slayer
Sepultura / and the two other projects by Max, i really love the guy
Pantera
Iron Maiden (not a huge fan)
Opeth
Savatage (underrated)
Gojira (i like them not only for their music but for their positive eco message)
Lamb of God (Randy Blythe also has a cool memoir about his detainment in Prague)
Fear Factory
Trivium
Testament
Nails (now this is extreme and heavy)
Alice in Chains (if that counts)
Also I like a few death metal bands…
Death
Hour of Penance
Aborted
I love Creed. Unfortunately they get almost as much hate as Nickelback gets, which I never understood. I always loved “higher” and “with arms wide open”