Alltorment is a thrash metal band from Goiânia, Goiás, active since 2012 and part of the Central-West Brazilian underground metal scene. They play in the direct, aggressive tradition of Brazilian thrash with limited studio output documented publicly.

Alma Negra is a heavy and thrash metal band from Curitiba, Paraná, formed in 2017. Operating within Curitiba's well-established southern Brazilian metal scene, the band delivers a raw, riff-driven sound rooted in classic thrash and traditional heavy metal.

Alma Siniestra is a thrash metal band from Río Cuarto, in Córdoba Province, formed by guitarist and vocalist Damián González, guitarist Nicolás Ortiz, bassist Luciano Villarreal, and drummer Salvador Velázquez. The band issued the ten-track demo "Origen" in 2012 and followed it with their debut full-length "Violencia extrema", released in January 2016, drawing on influences from Kreator, Sepultura, and Pantera.

Ambivalentt is a groove and thrash metal band from São Paulo, Brazil, formed in 2018. The band released a self-titled EP in April 2018, drawing on the city's rich tradition of crossover and groove-inflected thrash. São Paulo's dense metal underground has long been a hotbed for thrash acts pushing toward heavier and more rhythmically aggressive territory, and Ambivalentt fits squarely within that lineage.

Amnistia is a thrash metal band from Itabuna, Bahia, Brazil, representing the northeastern corner of the country's thrash underground. The band plays aggressive, no-frills thrash with a regional identity that separates them from the São Paulo-centric thrash wave that produced acts like Sepultura and Ratos de Porão. Itabuna, a city in the interior of Bahia, has a small but dedicated metal scene, and Amnistia has been an active presence in it since their formation.

Amonicide was a thrash metal band from Brasília, Brazil, active from 2019 until their split-up. Hailing from the Brazilian capital — a city with a smaller but dedicated underground metal scene compared to São Paulo or Belo Horizonte — they operated as an independent act within the country's thrash tradition.

Anarchus is a death/thrash metal band from Belo Horizonte, Minas Gerais, Brazil, active since the late 1980s in the city's vibrant extreme metal underground. The band recorded demos including "Total Hate" (1988) and "Melody's of Destruction" (1989), and released the compilation "Increasing the Hate" in 1997 marking a decade of activity. Their raw, aggressive style reflects the first wave of Brazilian extreme metal emanating from Minas Gerais.

Ancestral Terror is a death/thrash metal band from Catalão, Goiás, rooted in the old-school extreme metal tradition with lyrical themes of religious corruption, war, and iconoclasm. The band issued their debut recording Hallways of Pain and later appeared on the 2016 split Bacchanals of Horror alongside Rio de Janeiro act Orgy of Flies through Warhemic Productions. They have been on hold since around 2013.

Ancesttral were a groove/thrash metal band from São Paulo active from 2003 until their split-up, drawing on classic US thrash influences — Metallica, Pantera, Slayer, Anthrax — while incorporating modern groove and alternative metal textures. Their discography includes the debut full-length The Famous Unknown (2007) and Web of Lies (2016), the latter a well-reviewed eleven-track album that showcased a heavier, more polished direction.