edit: i am going to start going through the comments and updating this list accordingly. didn't expect so many lol, but happy to aggregate leftist music projects.
BLACKWATER SNIPER - a fusion of speedcore, noise, and extreme metal/punk. lyrical content is anti-war and anti-imperialist.
Blue Scholars - smooth and silky revolutionary jazz rap
CHOP CHOP CHOP CHOP CHOP CHOP CHOP - more noisy electronic metal. i've only listened to his debut, Extreme Creep. has a track on it protesting ICE, released nearly 6 years before the 2nd trump admin.
Christ vs. Warhol - a goth / deathrock band. Dissent touches on anti-capitalism quite a bit.
Emma Goldman - i feel like the name sums it up. queer anarchist screamo.
fromjoy - unique, VERY angsty vaporwave-infused metalcore. including them on this list is a bit of a stretch, but i really enjoy and recommend them. their song "machine" on their self-titled LP is anti-cop.
Godspeed You! Black Emperor - probably one of the most well known on this list. GY!BE is an anarchist music collective that makes instrumental post-rock. their latest untitled album is a protest album against the genocide in palestine.
Machine Girl - another comparatively more known project. digital hardcore. my favorite release of theirs is the metal-tinged U-Void Synthesizer. the song "Fortress Destroyer" off that album is about killing nazis.
Midori (Spain) - jungle / digital hardcore with occasional samples about anarchism
Orchid - anti-capitalist screamo/emoviolence
Panopticon - atmospheric black metal. one of the more well known faces in the RABM (red & anarchist black metal) movement. stopped sharing lyrics after the Kentucky LP. a lot of his lyrics on that album are about the miner strikes and early labor movement in kentucky.
Pig Destroyer - grindcore band. ceased writing political lyrics very early in the band's lifetime. Head Cage has an anti-cop song though.
Primitive Man - sludge metal band. genuinely a contender for the heaviest band of all time:tm:. a good portion of their lyrics on Caustic are anti-capitalist.
Pyrrhon - avant-garde, technical, dissonant metal band. Exhaust has a few political lyrics.
Sankara - communist vegan war metal. named after thomas sankara.
Thou - diy anarchist sludge metal. GREAT music, but sometimes a little sketchy. kinda gives egoist vibes
Vermin Womb - grindcore project related to primitive man
This is a very good list, Blackwater Sniper is painfully overlooked
Also saw GY!BE a few weeks ago, absolutely amazing live.