Atlantis is a traditional heavy metal band from Jaraguá do Sul, Santa Catarina, Brazil, formed in 2007 and signed to Classic Metal Records. Drawing on New Wave of Old Heavy Metal influences, the trio — Tino Barth, Bruno Eggert, and Fellipe França — explore occult and mythological themes across albums including their self-titled 2020 record, "Power in Our Hands" (2023), and "Volume II" (2025).

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 Fear was a death metal band from Timóteo, Minas Gerais, with roots tracing back to 2007 before the band reconstituted in the early 2010s. The group released the EP "Globaritarian" in 2013 and earned a foothold in the regional underground scene with politically charged lyrics delivered over aggressive death metal, performing at festivals including Grito do Rock in their home city before eventually splitting up.

Atomic Head was a speed metal band from Santiago, Chile, formed in 2004 by guitarist and vocalist SEbG with a focus on Bay Area thrash influences. The band released a self-titled five-track EP in 2006 and their only full-length album, March of the Urban Zombies, in 2014 before disbanding.

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.