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.

Atro is a blackened doom and death metal project from Campina Grande, Paraíba, active since 2019. The project operates in the underground extreme metal circuit of Brazil's northeast, blending the suffocating weight of doom metal with blackened atmosphere and death metal aggression.

Atropelo is a crossover thrash band from Mauá, in Greater São Paulo, whose influences include Brazilian hardcore/thrash veterans Ratos de Porão, D.F.C., and Cólera. The four-piece released their debut album "Mentira Acima de Tudo, Ilusão Acima Todos" in February 2025, recorded at Hells Pass studio in São Caetano do Sul, with lyrics in Portuguese addressing political and social grievances.

Atropina is a death metal band from Teutônia, Rio Grande do Sul, founded in 1996 and one of the more enduring names in the gaúcho extreme metal underground. Starting with a thrash/hardcore edge on their 1998 demo "Louvar a Tudo por Nada" and the 2001 debut "Santos de Porcelana," the band evolved toward brutal death metal, later releasing conceptual albums including "Mallevs Maleficarvm" (2014) — which addressed the Inquisition — and "Prego em Carne Podre" (2021), with Portuguese-language lyrics consistently attacking organized religion and authoritarian structures.

Atrorium is a symphonic metal band from Teresina, Piauí, formed in 2018, representing an outlier in Brazil's northeast metal scene by pairing orchestral arrangements with heavy guitar work. The lineup features vocalist Camila Morais, keyboardist Cassio Carvalho, and guitarist Flavio Anderson, and the band operates independently in a region with relatively limited metal infrastructure.

Atroz is a heavy and progressive metal band from Juiz de Fora, Minas Gerais, with roots going back to 1998 under various configurations. Their self-titled 2021 release on Bandcamp marked a renewed presence, and the band draws on a range of heavy and progressive influences rooted in the fertile Minas Gerais metal tradition.

Atrymo is a death and black metal band from João Pessoa, Paraíba, formed in 2017 by members with roots in prior extreme metal projects. The four-piece — featuring Aracélio on drums and vocals, Ivan on bass and vocals, Ivaldo and Bruno on guitars — channels themes of human hatred, greed, and spiritual corruption through tracks like "Sentidos Infames," "Miséria e Ódio," and "Depressão," with lyrics sung in Portuguese.

Attma is a death and groove metal band from Parnaíba, Piauí, active since 2020 and part of a small but growing extreme metal community in Brazil's northern coast. They blend the rhythmic heaviness of groove metal with death metal extremity, operating independently in a state better known for Teresina's scene than for coastal metal activity.