invented it.

refined it.

defined it.

were metal until they were all killed and replaced by robots sometime in 1991.  Strangely, Dave Mustaine has managed to retain his metalness, or metalocity, if you will.  Although, someday, Mustaine and the Lars Ulrich robot are gonna eat each other's heads.

Any L.A. band following in the wake of  is not metal, with the exception of  who were actually around pre-Crüe, just nobody outside of Hollywood knew about 'em.

is not metal, and at this point, not even rock 'n' roll, except for Ace Frehley who was/is/will always be cool as all fucking get-out. 

D.R.I. and Suicidal Tendencies are punk bands that became metal.  Entombed is a metal band that became punk and then reaffirmed their faith again in act of satanic bestiality so severe and offensive that we cannot even speak of it.

Neil Young, Iggy Pop and Roky Erickson are not metal but they could be if they wanted to.

is metal and to say otherwise will cause spontaneous inner-bleeding and fire of the spleen.

is rock 'n' roll but Lemmy is metal.  Not sure how that happened.

If you're not sure if your favorite band is metal or not, you can refer to these helpful tips:

1.  If any member of the band is named after a demon or god in Christian theology, any of H.P. Lovecraft's "Elder Gods" or any viking/pagan deities they are metal.

2.  One guitar is hard rock, one rhythm and one lead guitar could be rock (AC/DC) or metal (Metallica, pre '91), twin lead guitars are metal, three guitars are southern rock.

3.  Any band whose name begins with "Bon" and ends with "Jovi" is not metal.

4.  Any band featuring a glockenspiel is not metal unless they spell it: glöckenspïel.

5.  If Scott "Wino" Weinrich is in your band, you are metal.  If Scott Weiland is in your band, you are not.  In fact, if Scott Weiland is in your band you are not even rock, you are shit.

I hope this has been helpful in clearing up a few things.