Hi! I’d recommend starting out with bands like Black Sabbath, Iron Maiden, Judas Priest, Metallica, Megadeth, Venom, Motörhead, etc. You can also find a lot of new music by just going to the “fans also like” section on a band’s Spotify page and just clicking around. There’s also a great video by Madi Danger called Intro To Metal (https://m.youtube.com/watch?v=gZkNL-5r4BI) which I think you should definitely watch. Btw if you want recommendations for heavier or more obscure metal bands lmk
As for learning about the history of the subculture itself, there are plenty of documentaries out there about different genres and bands. One of my favs is called Murder in the Front Row and it’s about the beginning of the Bay Area thrash scene (you can find it on youtube for free I think)
There’s also a website called Map of Metal which has a lot of info about different subgenres.
Also, if you like System of a Down and Slipknot you should definitely check out Get Some by Snot. I think you might also enjoy Entombed’s Wolverine Blues. :)