You want to open a can of awesomeness? Well you got it. This is by no means an exhaustive list nor any that covers the whole spectrum. Some bands are serious others much more lighthearted. Generally all of these have strong folk metal influences drawing inspiration from the middle ages (fall of Rome to fall of Constantinople). Go wild. If I were to do a "top five tracks" from a few bands I would choose Cruachan, Heidevolk, Månegarm and Skálmöld

Cruachan - irish/celtic

Eluveitie - celtic gaul

Feuerschwanz - german "high medieval"

Equilibrium - german

Heidevolk - dutch

Norse/Viking (here I just dump a bunch) - Amon Amath, Brothers of Metal, Ensiferum, Månegarm, Skálmöld, Tyr

Alestorm - PIRATES, a humorous bonus for the funzies