A.D.H.E.R. is a heavy/thrash metal band from Río Grande, Tierra del Fuego, whose name is taken from the title of a Hermética song. The band released the album De otras tierras, recorded and mixed in Tierra del Fuego in 2006 and issued in 2007 through Argentina Thrash Metal, reflecting the raw, isolated energy of Argentina's southernmost metal scene.

Aamonhammer is a black/thrash metal band from Belo Horizonte, Minas Gerais, emerging from the same fertile extreme metal underground that produced Sarcófago and Sepultura. The band pursues a raw, aggressive fusion of black and thrash metal rooted in the early Brazilian extreme metal tradition. They are listed as split-up on Metal Archives.

Abatter is a heavy/thrash metal band from Florianópolis, Santa Catarina, formed in 2018 and currently on hold. The band plays a straightforward blend of old-school heavy metal and thrash, operating out of Florianópolis — a coastal city that has produced a modest underground metal scene largely overshadowed by larger Brazilian metal centers. Their Bandcamp page documents their recorded output before activity was suspended.

Abomination is a thrash metal band from Brasília formed in 2015, operating in the underground tradition of the Brazilian federal capital's metal scene. Playing aggressive, no-frills thrash metal, the band carries on the South American extreme thrash legacy in a city better known for bureaucracy than brutality.

Abortismo is a crossover thrash/punk band from Glew, Buenos Aires Province, featuring vocalist Lazaro Infante, guitarist Ariel Zurita, and the Marmet brothers on bass and drums. The band released their self-titled EP in February 2019, recorded and produced by Damian Nayar at Neurótico Records in Buenos Aires.

Absoluto Poder was a death/thrash metal band from São Paulo, Brazil, formed in 2013 by members Mike Dorsal and Rafael Tortuguita, drawing influence from Sodom, Dorsal Atlântica, and old-school Sepultura. The band blended the aggression of Brazilian thrash with death metal heaviness in the vein of early Death and Autopsy, releasing a demo titled 'When Your Nightmares Come True' in 2015 and working toward a full-length before splitting up.

Abstract was a heavy/thrash metal band from Anápolis, Goiás, Brazil, active during the 2000s within the state's growing underground metal scene centered around the annual Anápolis Metal festival. The band played straightforward heavy and thrash metal rooted in the classic Brazilian tradition before splitting up.

Abyss Angel is a black/thrash metal band from General Roca, Río Negro, Argentina, formed in 2024. The band released the track "metamorphosis" in December 2024, establishing themselves as a new entry in Patagonia's extreme metal underground.

Abyssal was a thrash metal band from Oliveira, Minas Gerais, Brazil, active from the early 2000s until their split-up. An independent act from the interior of Minas Gerais, they played in the classic Brazilian thrash tradition before disbanding with minimal widely documented releases.