Ancienterror is a death/thrash metal band from Santiago, Chile, formed in 2002 from the ashes of Missing Sequence, and has remained active in the city's underground scene ever since. The band released the EP "Arguments for Aggression" in 2007 and has built its lyrical identity around anti-religious, anti-globalization, and anti-capitalist themes.

Ancillae is a death/thrash metal band from Carazinho, Rio Grande do Sul, Brazil, formed in 2024. A recent entry into the Brazilian extreme metal underground, they combine the brutality of death metal with the aggression and riff-driven attack of thrash.

Andralls is a São Paulo thrash metal band formed in 1998 (active as a recording act from 2000), whose name references the historic Andraus building fire that killed 16 people in the city in 1972. Known for a self-described "fasthrash" style that pushes the tempo to near-death metal extremes, they have released albums including "Massacre, Corruption, Destruction" (2000), "Inner Trauma" (2005), "Breakneck" (2012), and "Bleeding for Thrash" (2019), the latter receiving a 9/10 from Metal Temple for its ferocious riff work and relentless aggression.

Anencefalo were a crossover thrash band from Santiago, Chile, active across several periods between 2004 and 2023, who evolved from punk-inflected death metal into a harder-edged thrash and crossover style. Their discography includes the albums "Odio" (2009) and "Cefalotripsia" (2011), with lyrics addressing mental illness, death, and depersonalization throughout their career.

Anestesia was a thrash metal band from Manaus, Amazonas, Brazil, formed around 1987 and active into the early 1990s as part of the first wave of Brazilian thrash. Operating out of Manaus — geographically isolated from the main São Paulo and Rio de Janeiro metal hubs — the band recorded a demo "Total Massacre" and contributed tracks to the Brazilian thrash underground, their themes centered on human and social concerns.

Anestesic is a thrash metal band from Santo Antônio de Posse, São Paulo state, Brazil, formed in 2008. Part of the continuing wave of interior São Paulo thrash acts, the band carries the aggressive, riff-driven sound rooted in the old-school Brazilian thrash tradition.

Anestesya was a thrash metal band from Garibaldi, Rio Grande do Sul, Brazil, formed in 2004 and named as a tribute to Metallica bassist Cliff Burton, directly referencing the instrumental "Anesthesia (Pulling Teeth)" from "Kill 'Em All." Blending 1980s thrash aggression with progressive and classical influences — a sound they called "Thrash/Heavy Progressive" — the band released the debut album "Cruel Fear" before eventually dissolving.

Anesthesia of Beer is a crossover thrash band from Campos dos Goytacazes, Rio de Janeiro, blending punk, hardcore, and extreme metal in the tradition of Brazilian crossover acts. Their discography includes the demo "Reign in Beer" (2009), the EP "The Lightning Broke My Bottle" (2012), the full-length "Altars of Drunkenness" (2017), and "My Terror Tapes" (2019), with lyrics spanning horror-film homage, beer-soaked party anthems, and sharp antifascist social criticism.

Aneurose is a thrash metal band from Lavras, Minas Gerais, whose sound pulls from classic thrash while incorporating death metal and hardcore elements. They released the full-lengths "From Hell" (2013) and "Juggernaut" (2016), as well as "Made in Rage", and have appeared on international tribute compilations covering AC/DC, Black Sabbath, and Sepultura, reflecting their standing in the Brazilian underground.