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.
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 battle 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.
BRUTAL DEATH METAL: The knight arrives, kills the dragon, kills the princess and THEN fucks her.
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. Next he impales the princess next to the dragon, sacrificing her to Satan.
SPEED METAL: Knight-kill-dragon-save-princess-fuck-her.
GRIND METAL: The knight arrives, shouts something perfectly incomprehensible during 2 minutes and sets off again.