emo + metal = hardcore

Nah. Hardcore was a sub-genre of punk that was somewhat defined by its faster tempo and more aggressive riffs and singing/yelling styles in the 80s. It then became its own genre and forked in the late 80s or early 90s into a more metal influenced movement (often called 'new school hardcore'), on the one hand, and a more post-punk sound, on the other hand. Emo came out of the post-punk scene, but as it developed took sounds and influence from new school hardcore, generating a sub-genre called Emo-core. Emo-core then became the predominant form of the Emo genre as the sound and styling took more and more influence from the new school hardcore scene.

Metal had its own parallel development, but it didn't develop in isolation. I can't give a great genealogy of it, but, for example, early thrash metal musicians (early 80s) were influenced by the speed and aggression found in early hardcore. I think Slayer was influenced by Dead Kennedys, Black Flag, and perhaps even Minor Threat.

next you're gonna tell me "daft punk" isn't punk

Everyone in is this is fat, so a better descriptor would be softcore.

wait if pink floyd isn't from the czech republic why do they call it "prague rock"?

Was cereal unavailable in this hellscape of a town?

Ditto. But it was flooded basements, punk rock record stores, apartment kitchens, office complex outdoor "common areas" (until they started putting locks on the power outlets), and alternative theater spaces. But never a Dennys that I can remember.

Warehouses that should have been condemned but instead housed both people and concerts

Yeah. Bowling alleys, vfw halls in small farm towns, empty store fronts, gnarly warehouse spaces, living rooms, pizza parlors, community centers, art spaces, basements, record stores, city parks where outlets were available, etc.

Salad days.