While Finland’s Ensiferum and Turisas, the Faeroe Islands’ Tyr and Switzerland’s Eluveitie subscribe to a common philosophy, they’re also different enough that you can actually tell them apart—thus solving a relatively frequent problem in the extreme-metal genre from which they borrow blast beats, growled vocals and severe riffage. Tyr’s music, for instance, has an austere grandeur that exactly matches the mental picture one would have of the Faeroes, rocky Danish-affiliated islands perched north of Scotland. “I’ve always liked the Scandinavian traditional melodies and ballads—we’ve done a lot of songs where we put heavy metal on a Faeroese melody,” Joensen says. “Since I went to music school, the way our music is harmonized is far more classical than what you would hear in other bands.” Eluveitie’s frontman, Chrigel Glanzmann, explains that his own group mixes “melodic-style death metal and Celtic folk music, which we play the traditional way.” Yes, that means live uilleann pipes, tin whistle and hurdy-gurdy.

But wait: Celts in Switzerland? Come on, how seriously can we take a band whose drummer is named Merlin? But Glanzmann’s connection to the material is bone-deep. “When you hear about Celtic traditions or fashions today, it mainly comes from the British Isles,” he says with a hint of regret. “But Switzerland was Europe’s main Celtic area. If you go wandering in the afternoon, you pass by the old heritage, like stone carvings. It’s had an impact on me ever since I was a little boy.” Ensiferum draws inspiration from Finland’s epic poetry and mythology, while Turisas dug deep to make 2007’s The Varangian Way, a wildly imaginative concept album about an 11th-century trade route between Scandinavia and Ukraine.

The fact that the Paganfest bands all mention soaking up ancient lore at a young age may explain why they play their music with considerable dedication and not a hint of condescension—this is no country for hipsters. And while it’d be easy to snicker at bands who pose in chain mail and for whom pimping a ride means decorating a handcart with skulls (“European folk goes back further than the one in America and can have dark implications,” Joensen says ominously), these groups display a level of passion and commitment that’s completely infectious. Plus, they do look good in that chain mail.

Yet this attachment to roots doesn’t mean the music is rigidly codified—for instance, Turisas once covered the 1970s disco band Boney M. “We can go from a big, symphonic, rousing theme to Balkan wedding music,” Nygård says. “We can even experiment around with electronics or more proggy stuff.” He laughs. “We have quite a healthy mess.” Indeed, fans of bands such as Gogol Bordello will be on familiar ground when hearing Turisas’s “In the Court of Jarisleif,” which is jet-propelled by a maniacal accordion—except the Finns’ speed and agility make Gogol Bordello sound drowsily sloppy. That energy, impressive enough on record, is decupled live, which is where folk-metal bands truly shine.

Indeed, in talking to these artists two themes reoccur frequently: an interest in the past and the desire to put on a hell of show—these warriors are wicked entertainers. Bare-chested and in kilts, the members of the mighty Ensiferum make a startling sight as they barrel through songs such as “Blood Is the Price of Glory” and “Deathbringer from the Sky,” and the rollicking Turisas plays decked out in pelts and body paint. “Onstage it’s really about being interactive with the audience and having a good time,” Nygård says. “And not being afraid to laugh at ourselves!”

Paganfest is at B.B. King Blues Club & Grill Thu, May 22.