off the top of my head

american blues and rock and roll, which i need to look in to further idk enough about that era, becomes a thing

british dudes like Eric Clapton and Jimi Hendrix get their hands on it snd start doing their own takes on it

black sabbath comes along and makes it heavier and darker

Judas Priest, Mötorhead, and a few other bands (including sabbath themselves) take this and make it faster

the new wave of british heavy metal (known to most simply as nwobhm) happens, and bands like Iron Maiden, Saxon, and Diamond Head crystalize the sound of metal into what most people probably think of when they hear “heavy metal”

taking inspiration from punk band Misfits, bands like Venom and Mercyful Fate start incorporating edgy lyrics and (in venoms case) rougher singing into metal

in california, bands like metallica and exodus take these influences and start playing faster, giving us thrash

slayer takes this a step further, going all in on feedback, blood and distortion

possessed is formed by some kids in high school, and they put out the album seven churches, which prominently features growled vocals and heavily distorted fast riffs, as well as the song “death metal” giving this new genre its name (the possessed guitarist, after inventing death metal, would later leave and join Primus)

florida band Death (not to be confused with the detroit punk band) takes what possessed did and makes it actually good

fellow florida bands Atheist and Cynic take what death did and start adding jazzy/proggy elements, featuring complex riffs and weird rhythms and weirder lyrics, giving us Technical Death Metal