It seems to me that metal and heavy metal are more or less interchangeable terms. In any event there are certainly heavier bands but if Metallica isn’t metal then nobody is. Especially albums like Ride the Lightning, Master of Puppets, and Kill em All.
Appetite isn’t quite metal but it wanders into that territory a bit. Like the cool riffs in It’s So Easy and the thrash-metal ending of Paradise City.
To me metal is that thick, distorted guitar sound, palm-muted riffs, and galloping rhythms at breakneck speeds.
If I had to pick one example to stick on a probe to launch into deep space to tell any alien who might find it what metal was, it would be this: https://www.youtube.com/watch?v=md3B3I7Nmvw
Slash is an amazing player with a gorgeous tone and the interplay between him and Izzy is telepathic, but they didn’t sound anything like that.
I loved Sabbath, Ozzy and Metallica growing up, as I got into college I transitioned into occasionally listening to Pantera, Tool, and (less often) Sepultura. Now I hardly ever listen to metal.
Is Tool metal? Progressive metal? Not sure on that one now that I think about it.
See, I think that both Poison and Mayhem took something silly and took it too far. Mayhem took it a whole lot too far, the prime example of someone taking themselves far too seriously.
I dunno, the serious/silly equation is complex in metal. Iron Maiden certainly are silly and a little pretentious, but they knew it, and I can accept them. Poison were silly and kind of took themselves seriously. They expected that career to last. Some members of Mayhem thought they were something more than a Metal band, which is a seriously maladjusted thing to do.
From me for asserting it? Or from Page/Plant/Bonham/Jones for committing it? 
I think it’s a question of the artist’s perceived attitude about the subject and themselves. Do they think they’re being important, meaningful or relevant with whatever they’re singing about, or are they just scratching that artistic itch? I can take all the ludicrous lyrical content that M.O.D./S.O.D. (or hell, Sabbath and Zeppelin) put out, because the persons themselves know they’re coming across as a caricature at best, and they (almost) behave like average people when not on the stage. Every time I hear Danzig get interviewed, I get the overwhelming sense he’s taken every lyric he’s sung seriously, even the ones that contradict the other ones.
Bwahahaha, the White Wizard video was great. And yeah, Metal is an attitude, and not just a sound. I understand that there’s some overlap between Aerosmith’s and Zeppelin’s sound, but no matter how hard Aerosmith might rock, they really wanted to be the Rolling Stones, a Rock 'n Roll band. I don’t think Zeppelin wanted to be just the Rolling Stones. Maybe you have to take yourself a little too seriously to be Metal.
Yes, IIRC, all of the first bumps featured S.O.D. I also remember another one from the first crop that used The March of the S.O.D. (warning, seamless one hour loop of sweet, pure, divine Thrash. Oww, my neck hurts. Thank god, a commercial.*) They were things of beauty. S.O.D. playing over old silent stock footage of things going terribly wrong - early flying machines disintegrating on the ground, cars jumping through barns, etc. Perfect.
Wow, somehow I’d never run into either of those. Thank you so very much.
I think this is where I have a problem with the historical revisionism. Metal being a distinct umbrella term is strange to me. WHEN I WAS A BOY…zzz… Metal was assumed to be strict old time Heavy Metal unless you were throwing modifiers in there to describe the distinct sub-genre. There was no Metal before Heavy Metal, and even if Zeppelin was no Blue Cheer, they were part of that first wave of metal. The Hard Rock bands were strictly Rock 'n Roll bands that played a hard version of Rock 'n Roll, and didn’t get into the half step chromaticism that well, I’m prejudiced, but I think has its roots in Surf Rock. Lots of people were fast before, but Dick Dale was the original shredder, and half steps (well not chromatic, but it sure wasn’t the blues) were his bread and butter.
And really, If Def Leppard gets to ever be Metal, how can you exclude Zeppelin or GnR’s first record? I distinctly remember a 17 year old me talking my way out of a girl’s unmentionables when I corrected her and told her that Appetite for Destruction was a Heavy Metal record, not a Punk Rock record. I agree that it was a tactical mistake, but I stand by it. Mr. Brownstone out-Metals Def Leppard on their most Metal day, even if they had an electric Metaling Machine. If I were to judge Hair Metal, I’d say that “Sweet Child 'o Mine” is probably its artistic pinnacle (apologies to Shagnasty if I am judging from ignorance). Not the Thrash Metal I loved at the time, but it had its roots back in the same bands.
Sorry about the marathon, footnoted, catch-up post (that I could make even longer), but it’s been a busy 24 hours. On preview: I’d consider Tool Prog Metal.
*Wow, their grooves just have a “rightness” about them to me. They’re the Metal equivalent of Parliament/Funkadelic grooves.
Excellent! Iron Claw is on Spotify too. 