Insannica is a metal band from Juiz de Fora, Minas Gerais, Brazil, founded in late 2010 with roots in thrash metal and a sound that has since incorporated groove metal, metalcore, hardcore, and progressive influences. The band has released original material including the track "Mitopatia" via their Bandcamp page, reflecting their eclectic, genre-blending approach.

Insecticida is an old-school thrash metal band from Timbaúba, Pernambuco, Brazil, playing aggressive 1980s-style thrash with no modern frills. The band infuses northeastern Brazilian culture into their music, including humorous lyrics that tackle social themes with regional irony, and released their debut EP "Deu a Mulesta dos Cachorro" in 2017.

Insidious Nature is a progressive/technical death metal band from São Luís, Maranhão, Brazil, formed around 2020 by vocalist Pitter Cutrim, guitarists Rogers Rocha and Luke Hellstrvm, bassist Lucas Abreu, and drummer Lucas Mano. Citing Death, Cynic, and Beyond Creation as primary influences, the band released the single "Doomed Epilogue" in 2022 and their debut album "A Prelude to the Endless" in June 2023.

Insomnio is a solo project founded in 2016 in Concepción, Chile by Francisco Acuña Inzunza, also known as the bassist of thrash/speed metal band Crushing Brain. The project blends neofolk, doom, and black metal with themes of melancholy, desolation, nature, and mortality, and has released a prolific run of albums since 2020 including Anónimo (2020), Canto a la desolación (2021), Umbrío (2022), and Danza silenciosa de su muerte (2023).

Insomnio Mutante is a thrash metal band from Chillán, Chile, active since 1998. They released their debut album Mundo Desconocido in May 2014, recorded at Estudios Decibeles between September 2013 and March 2014.

Insorcist is a death/black metal band from Santiago, Chile, originally formed in 2002 under the name Azael before adopting the current name and recording the three-track demo Donfallen Kingdom in 2003. The band released the EP Eternal Torment in 2006 and their debut full-length The Slaughter of Divine Creed in 2011 through Apocalyptic Productions, a nine-track concept album recorded at Sade Studios with lyrics exploring anti-Christian and occult themes.

Instep is a thrash/death metal band from Vila Velha, Espírito Santo, Brazil, formed in 2021. The band released their self-titled "Demo 2021" on Bandcamp in June of that year, a four-track recording featuring tracks such as "Total Destruction of the Nation" and "One Bit."

Instinto Ruim is a grindcore band from Recife, Pernambuco, Brazil, whose lineup includes Diego (vocals), Jonathas (drums), and Raphaell (guitar). The band released a six-track demo in 2019, drawing on metal, hardcore, crust, and grindcore influences in the tradition of the Brazilian extreme underground.

Insulter was a Brazilian death/thrash metal band from Belo Horizonte, Minas Gerais, formed in 2012, working in the same extreme underground tradition as early local acts like Sarcófago and Sextrash. Their demo recordings were compiled and released in 2015 by Nuclear War Now! Productions on the album "Blood Spits, Violences and Insults," which also appeared on Iron Bonehead Productions in a gatefold LP edition.