fundametals

Some Examples:
Master of Puppets and Reign in Blood are two of the best albums ever.
Black Sabbath are the grandfathers of metal.
Linkin Park is not metal. They are alt pop.
Nu Metal, like all metal subsets, is full of good music.
If you go to a metal show, there will always be a smell of weed in the air. It doesn't necissarily have to come from you, but it will be there.
Say "Up the Irons" for Iron Maiden.
Don't try to list all the subsidiaries of metal. You will be counting forever.
Some popular subsidiaries include: Death Metal, Thrash Metal, Nu Metal, and Power Metal.
It can always be much louder.
There is no one dominant instrument. Even bass is important. Don't believe me? Listen to For Whom the Bell Tolls by Metallica.
Hair Metal isn't metal.
Not all good metal is European.
Dethklok is both a real and a fake band.
Not all metal is about death. Just most of it.
Double Bass always sounds cool.
Songs that are slow are ok as long as they pick up at some point.
You can growl, scream or sing. It's up to you. It isn't up to the subsidiary. I've heard death metal bands with clean vocals.
Don't call yourself a metal head if all you know is "One" from Guitar Hero III. Do some research.

Metal is a great form of expression. Just remember to have fun.
These are all fundametals.