Sosterik is a Pittsburgh heavy/thrash metal band formed in 2018, channeling the blue-collar intensity of Pennsylvania's industrial heritage into a hard-hitting blend of classic heavy metal and thrash.

Spectral Sorcery is a Pennsylvania psychedelic doom and stoner metal band formed in 2023, crafting slow, haze-drenched heavy music that prioritizes atmosphere and lysergic texture over aggression. Their sound draws from the fuzzed-out, riff-worshipping traditions of desert rock and occult doom.

SpellBook is a heavy metal and hard rock band from York, Pennsylvania, formed in 2020, playing classic-influenced heavy metal with a foundation in hard rock dynamics and traditional song structures.

Spesimin is a Philadelphia-based band formed in 2020 that fuses thrash metal aggression with death metal heaviness and punk rawness, cutting through the city's underground with a no-frills cross-contaminated attack.

Spider Control Rod is a death metal band from Coopersburg, Pennsylvania, formed in 2024, adding a new and abrasive voice to the state's densely populated extreme metal underground.

Spike the Tomb is a Pittsburgh melodic death metal band formed in 2012, weaving Gothenburg-influenced melodic leads and twin-guitar harmonies through a backbone of forceful American death metal.

Spinebelt is a groove metal band from Grantville, Pennsylvania, formed in 2020, delivering mid-paced, chug-heavy riffs in the vein of early 1990s groove metal with a straightforward and punishing approach.

Spirit Flaw is a Philadelphia thrash and crossover band formed in 2020, combining the aggression of hardcore punk with the riff-driven attack of thrash metal in the tradition of East Coast crossover.

Spirus is a Philadelphia black/thrash metal band formed in 1996, one of the city's longer-running underground metal acts, fusing the speed and riff density of thrash with the cold aggression of black metal.