Steve 'n' Seagulls may play in the styles of American country, roots and bluegrass music, but the Finnish quintet might as well be an honorary hard rock and metal band.

The band broke out in 2014 after a YouTube video of theirs -- a cover of AC/DC's "Thunderstruck" -- went viral. To date, it has racked up more than 27 million views. The eruption of popularity translated into a U.S. tour the next year and an album full of "hillbillified" versions of hard rock and metal tracks such as Iron Maiden's "The...