Viking metal is folk metal with Norse leanings, in my opinion. But still, an amazing genre (and my favorite):
Bathory (the fucking founders; Hammerheart and beyond)
Turisas (might be the most accessible Viking metal band)
Ensiferum (another accessible band)
Thyrfing
Equilibrium
Einjerhar (old-school Viking metal)
Borknagar (self-titled and The Olden Domain)
Finntroll (not Viking metal; but good folk metal)
Tyr (not my favorite band; they're kinda boring; but still, they have some good hooks)
Lots more, but I'm a bit preoccupied at the moment. I'll list more later, if I think of any. Was this even a request for recommendations?