The story is, there's a beautiful princess trapped in a castle guarded by a dragon. This is how the story would play out, depending on the metal genre of the knight:
POWER METAL: The protagonist arrives riding a white unicorn, escapes from the dragon, saves the princess and makes love to her in an enchanted forest.
THRASH METAL: The protagonist arrives, fights the dragon, saves the princess and fucks her.
HEAVY/CLASSIC METAL: The protagonist arrives on a Harley, kills the dragon, drinks a few beers and fucks the princess.
FOLK METAL: The protagonist arrives with some friends playing accordions, violins, flutes and many more weird instruments, the dragon falls sleep (because of all the dancing). Then they all leave without the princess.
VIKING METAL: The protagonist arrives in a ship, kills the dragon with his mighty axe, skins the dragon and eats it, rapes the princess to death, steals her belongings and burns the castle before leaving.
DEATH METAL: The protagonist arrives, kills the dragon, fucks the princess and kills her, then leaves.
BLACK METAL: The protagonist arrives at midnight, kills the dragon and impales it in front of the castle. Then he sodomises the princess, and drinks her blood in a ritual before killing her. Then he impales the princess next to the dragon.
GORE: The protagonist arrives, kills the dragon and spreads its guts in front of the castle, fucks the princess and kills her. Then he fucks the dead body again, slashes her belly and eats her guts. Then he fucks the carcass for the third time, burns the corpse and fucks it for the last time.
DOOM: The protagonist arrives, sees the size of the dragon and thinks he could never beat him, then he gets depressed and commits suicide. The dragon eats his body and the princess as dessert. That's the end of the sad story.
PROGRESSIVE (PROG) METAL: The protagonist arrives with a guitar and plays a solo of 26 minutes. The dragon kills himself out of boredom. The protagonist arrives at the princess' bedroom, plays another solo with all the techniques and tunes he learned in the last year at the conservatory. The princess escapes looking for the HEAVY METAL protagonist...