Athkan is a groove and thrash metal band from Salta, Argentina, formed in 2013 by guitarist Gustavo Díaz and bassist Sergio Ruiz. Drawing on the post-thrash heaviness of Pantera and Meshuggah, the band released two records in 2013 — the album Walking Through Fear and the compilation Simbiosis — with vocalist Mauro Espínola and drummer Eduardo Fernández rounding out the lineup.

Athron was a Brazilian death/thrash metal band active in the 2010s before splitting up. Playing in the aggressive tradition of Brazil's extreme metal underground, the band combined the riff-driven attack of thrash with the heavier, darker tonality of death metal.

Atomic Blast is a thrash metal band from Parnaíba, Piauí, formed in 2012 and active in Brazil's northeast underground metal scene. Playing aggressive, riff-forward thrash in the tradition of the Brazilian thrash movement, the band has maintained a presence on regional circuits since their formation.

Atomic Roar is a thrash metal and metalpunk band from Rio de Janeiro, formed in 2003, featuring Victor Whipstriker of the punk outfit Whipstriker on bass alongside Vinícius Hellpreacher, Victor Poisonhell, and Léo Witchcaptor. The band deals in raw, street-level thrash with strong punk crossover energy, documented across four studio albums — "School of Lust" (2006), "The Warfare Merchants" (2009), "Atomic Freaks" (2011), and "Never Human Again" (2017) — as well as numerous split releases with bands from the global underground.

Atomic Spell is a black/thrash metal band from Santa Marta, Magdalena, Colombia, formed in 2022. The band released a demo, "The Persistent Onslaught of the Witch," in 2023 followed by the EP "Nuclear Speed Ritual" in 2024, playing under the Unsigned/independent banner with themes of death, blasphemy, and rock 'n' roll. The band suffered a loss when guitarist Ricardo Goenaga Ferro passed away in 2025.

Atomic Thrash is a thrash metal band from Rio de Janeiro, formed in 2014 and currently on hold. Operating within the city's active underground thrash scene, the band plays aggressive, old-school thrash metal in the tradition that Rio de Janeiro — a foundational city for Brazilian extreme metal — has long cultivated.

Atria was a thrash metal and metalcore band from Maricá, Rio de Janeiro state, formed in 2020 and short-lived. Blending the riff aggression of thrash with metalcore's structured heaviness, the band were part of the broader metal underground in the greater Rio de Janeiro region before disbanding.

Atrito Urbano is a crossover thrash band from Natal, Rio Grande do Norte, formed around 2012–2013. Their Portuguese-language lyrics tackle social and political themes, and their discography includes the EP "Aprendiz de Escravo" (2014), the split "Infecção Urbana" with Infected, and the album "Praga Disfarçada" (2016), all self-released through independent channels.

Atrocitus is a thrash and metalcore band from Curitiba, Paraná, one of the more active names in the city's underground metal scene. Drawing on aggressive thrash structures alongside metalcore dynamics, the three-piece — featuring Huan Cruz on vocals and bass, Geert Giullian Strijker on guitar, and Pettrus on drums — has released singles such as "Veneno" and "Repulsa" and built a following through energetic live shows across the Paraná metal circuit.