Five Finger Death Punch.

BloodEagle

Some modern metal/rock which I would recommend and wouldn't alienate someone coming from the lighter side of things too much - 

Oathbreaker
Power Trip
Amenra
Baroness
Neurosis
Sumac and or Isis
Yob
Melvins

Reverend

Early Baroness was fantastic and really heavy. Newer stuff still good but obviously a bit different.

Bolzer are incredible.
Tau Cross I keep going back to.
Morbus Chron, Tribulation, Execration, In Solitide, Obliteration and Nekromantheon all killer.

Last year's ep from Rid was also brilliant.