To understand the difference between metal and rock, let's imagine a situation and see how each style will resolve that question:

"In a tower, at the top of the castle, there’s a beautiful princess, locked and guarded by a great and terrible dragon" ...


HEAVY METAL:
The protagonist arrives to the castle on a Harley Davidson, kills the dragon, gets drunk with the princess and then fuck with her.

MELODIC METAL:
The protagonist arrives at the castle in a white winged horse, escapes from the dragon, saves the princess, fleeing away and make love with her.

THRASH METAL:
The protagonist arrives to the castle, kills the dragon, and fuck with the princess.

POWER METAL:
The protagonist arrives branding his sword and hangs a glorious battle against the dragon. The dragon succumbs as he stands, bathed in the blood of his enemy, a sign of triumph. Rescues the princess. Exhausted her patience with self-praise and fucks her.

FOLK METAL:
The protagonist arrives accompanied by several friends and goblins playing accordion, lute, viola and other weird instruments. Make the dragon sleep after so much dancing, and leave without the princess because the forest is full of nymphs, elves and fairies.

VIKING METAL:
The protagonist arrives in a ship, kills the dragon with an axe, bake and eat. Rapes the princess, pile the castle and toss fire in everything before he go.

DEATH METAL:
The protagonist arrives, kills the dragon, fucks the princess, kill the princess and leaves.

BLACK METAL:
Arrives at dawn with the fog. Kill the dragon and impales her in front of the castle. Sodomizes the princess, cut with a knife and drinks her blood in a ritual before killing her. Then he discovers that she was not a virgin and impales her with the dragon.

GORE:
Arrives, kills the dragon. Climb the castle, fucks the princess and kill her. After that, he fuck her dead body again. Burn the body of the princess and fucks her again.

SPLATTER:
Arrives, kills the dragon opens it with a scalpel. Sodomizes the princess with the guts of the dragon. Open holes in her with a scalpel and rapes each hole. Take off her eyeballs and rapes the princess orbits. After killing the princess, he dissects, takes pictures, and released an album whose the cover is a picture of it.

DOOM METAL:
Arrives at the castle, look at the size of the dragon, gets depressed and kill himself. The dragon eats the corpse of the protagonist and then eats the princess.

WHITE METAL:
Arrives at the castle, exorcised the dragon, takes the princess and uses the castle to host another Church of his faith.

NEW METAL:
Arrives at the castle thinking he is THE CHOSEN ONE and shouting bravado. Want to prove to everyone that he is cool and able to save the princess. Thinking he can beat the dragon; loses badly and takes his groins kicked. New Metal protagonist takes Prozak and goes to record an "The Best Of " album.

GRUNGE:
Arrives in drugs, escapes the dragon and find the princess. Tells her about his sad childhood. The princess punch him in the face and goes to find the Heavy Metal protagonist. Grunge protagonist suffers a heroin overdose.

CLASSIC ROCK:
Arrives in a bike, smoking marijuana, and offers it to the dragon, who soon becomes his friend. After camping with the princess in a far side of the garden, and after a lot of sex, drugs and rock'n'roll, has an overdose of LSD and suffocated on his own vomit.

PUNK ROCK:
Arrives kicking the door, spitting in the dragon, throws a rock and flees. He make a graffite on the wall of the castle with anarchy "A ". Makes a Mohawk haircut in the princess and then opens in a fanzines tent in the lobby of the castle.

EMOCORE:
Arrives at the castle and tells to the dragon how much he likes the princess. The dragon takes pity and let him pass. After entering the castle he discovers that the princess escaped with the Heavy Metal protagonist. Write a letter emotive song telling how he was abandoned by his beloved and the world is unfair.

PROGRESSIVE:
Arrives the castle, playing a virtuous 26 minutes guitar solo. The dragon kills himself in boredom. He find the princess and plays another solo that exploits all the techniques of atonality into ternary bars learned in the last 3 years of the conservatory. The princess escapes and run behind the Heavy Metal protagonist.

HARD ROCK:
Arrives in a red convertible with two busty blondes and drinking Jack Daniel's directly in the bottle. Kills the dragon with a knife and makes an orgy with the princess and the blondes.

GLAM ROCK:
Arrives at the castle. The dragon laughed so much when he see him and let he pass. He enters the castle, steals the princess hair dresser and lipstick. Then convinces her to paint the castle to pink, and change her hair color.

INDIE ROCK:
Enter by the castle’s backdoor. The dragon felt guilty about want to hurt that skinny nerd with glasses and let him pass. The princess cannot hold and stand to hear him talking about fashion and films, and flees with the Heavy Metal protagonist.