Hahaha, Matt, you would be surprised at what kind of sub genres are out there. take this, "kindergarten metal" hahaha, pretty funny. Pirate metal i just some stupid genre some idiot thought of, just like Emma did with "Beer Metal"...omg...she heard vodka, and Korpiklanni's songs are liquor inspired, so she thought, "oh what the hell, lets call it beer metal.
lol. Pirate metal and Beer metal, and variations of Folk/viking/and power. But then again, who chooses the genres? Bands create them themselves, but only if their music is completely different and new. Maybe Pirate metal was inspired with the pirate-like vocals. Who knows. Ill try and find something on the net about it.