An accordion can turn the most straightforward and mainstream compositions into wholly unique works.  The instrument almost demands a kind of "What if...?" approach to considering genre: 

What if... you constructed a rap beat from an accordion loop? 

What if... you covered some mainline pop hits with a Polka band? 

Or even "What if... you added an accordion to heavy metal?"  Well, that's what "folk metal" is all about!

One of the top bands in the sub-genre is Turisas.  Although the band has been active since 1997, it's their post-2004 work, starting with the album "Battle Metal", that accordion players should consider giving a listen, even if you've ever been interested in heavy metal. 

This is when Turisas started including Finnish accordionist Janne Mäkinen on their studio work.

On first impression, the band probably strikes the listener as being... well... silly.

Watching the music videos the band has produced, you almost wonder if you're supposed to laugh as the band, dressed in their best renaissance festival gear, pretend to clobber one another with broadswords and pointed staffs. This seems to come with the territory when it comes to that style of metal rooted in Viking mythology. Needless to say, the interesting thing about Turisas isn't their wild costumery or live action Dungeons and Dragons reenactments, but the often-times surprisingly skillful musicianship put on display by some of their members, especially Janne Mäkinen.

Leaning towards symphonic rock, the band's initial inclusion of accordionist Janne Mäkinen almost seems like an afterthought, as if the band said to themselves "Let's get every single instrument we can think of in there!"  Indeed, there are points on "Battle Metal" where Mäkinen's accordion playing seems to be fighting to stand out in the cacophony of sounds surrounding him.

This is, honestly, what makes it so interesting, though.  Accordionists are used to taking part in genres of music where the accordion is king.  Tejano and polka simply wouldn't exist without accordions; and even zydeco, which leans towards the more free-form and collaborative nature of jazz, still relies heavily on the sound of an accordion for its unique flavor.

Metal on the other hand is a genre that doesn't traditionally use, and arguably doesn't need, accordions; so hearing Mäkinen play loud and fast and hard on the accordion, trying to make it more noticeable in the barely-controlled chaos that dominates the band's sound, results in a play-style that you're probably never going to hear in traditionally accordion-oriented music.  Maybe accordion was never meant to sound this aggressive, but nevertheless, Turisas is a fascinating oddity for accordion fans, if nothing else.

Interestingly, and perhaps not surprisingly, Mäkinen left the band in 2008.  Perhaps he was feeling that his considerable skills as an accordionist were not really being put to their best use in the context of a loud, chaotic metal band.  In any event, "Battle Metal" and "The Varangian Way" remain an interesting listen for anyone who's ever wanted to hear accordion played quite differently than we're used to.