Indisposed was an all-female thrash metal quartet from La Plata, Argentina, formed in 2013, with members Pely Macchi on vocals, Anahí Fernandez on guitar, Salo Astudillo on bass, and Laura on drums. The band released two EPs, "Hangover" (2015) and the self-titled "Indisposed" (2017), both rooted in classic 1980s thrash with high-energy tempos and sharp twin guitars.

Infectai is a speed/thrash metal and crust band from Florianópolis, Santa Catarina, Brazil, formed in 2012 by André (vocals), Murilo (drums), Aranha (guitar), and Sapo (bass). Drawing on the raw energy of 1980s punk and metal, the band writes music with explicitly critical content targeting contemporary economic and social systems. Their self-titled EP, released in October 2012, contains four tracks including "Frutos de Um Problema Social" and "Escravo do Inferno."

Infected Cells is a death/thrash metal band from Simões Filho, Bahia, Brazil. The band released their debut EP "Voices from the Hell" in 2018, recorded between 2015 and 2017 at WR Bahia Studios in Salvador, Bahia; the seven-track EP was later released on cassette in 2022. They followed it with the EP "This Is the End" (2020) and a live album documenting their appearance at Dopesmoke Festival in 2021.

Infected Mind was a death/thrash metal band from Campina Grande, Paraíba, Brazil, signed to the InfernalFox label. The band recorded their album "Rascals of Destruction" at Ponto Som Studio in Campina Grande, which includes a live bonus track — a cover of Black Sabbath's "Into the Void." Their lyrical themes centered on social issues and injustice.

Infernal Atröz is a black/thrash metal band from Blumenau, Santa Catarina, Brazil, formed in 2022 and rooted in Satanic themes. The band released a debut single-demo in January 2023, followed by the track "A Noite da Caçada" and a full demo in 2024. They operate as an unsigned independent act within southern Brazil's underground extreme metal scene.

Infernal Hate is a thrash metal band from Ijuí, Rio Grande do Sul, Brazil with a long-running presence in the country's underground metal scene. The band's discography includes the full-length Upset (2008) and the demo ...See Me Come (2022), both catalogued in the Encyclopaedia Metallum. They remain active as an independent act within Brazil's southern thrash metal underground.

Inferno Nuclear is an old-school thrash metal band from Belém, Pará, Brazil, formed in 2007 under the name Old School Attack before adopting their current name. Drawing heavily from the Bay Area and German thrash traditions — citing Exodus, Testament, Kreator, and Sodom as key influences — the band features vocalist Wellington Freitas alongside rotating members including guitarist Alexandre Durães. Their 2021 album Diante de um Holocausto was recorded at Chaar Estúdio in Belém and stands as one of their most fully produced releases.

Infestatio is a thrash metal quartet from Jundiaí, São Paulo, Brazil, featuring Rafael "Rafão" Neves on guitars and vocals, Reginaldo "Regi" Iobbi on guitars, Diego "Negão" Necromancer on bass, and André "Fanta" on drums. The band blends old-school and modern thrash approaches with groove-driven riffs and semi-aggressive vocals that draw comparisons to acts like Sadus. Their EP F.Y.A., a five-track release produced by Rafão and recorded partly at Jardim Elétrico Studios, drew favorable coverage from Brazilian metal press on its release.

Insanity was a death/thrash metal band from Fortaleza, Ceará, Brazil, formed in 1989 under the name HON (Hexistence of Noise) by bassist/vocalist George Frizzo and guitarist Alberto Lopes before adopting the Insanity name later that year. The band released the demo "In Search of Reason" in 1990, recorded at Proaudio Studios in Fortaleza, and later issued the full-length "Phobia" in 1993 through Muvuca Records before splitting up in 2003.