Masterhead are a three-piece thrash metal outfit from the Fortaleza metropolitan area whose sound draws heavily from the Bay Area tradition, with Francisco "Mustaine" Alves handling both guitar and vocals alongside Denilson Andrade and John Nascimento. They built their catalog through the 2008 demo Enemy of Time and the 2017 EP Waiting Terror, later releasing the single Metal Warrior in 2021.

Mastermind Unlimited are a heavy metal band from Nova Iguaçu who debuted with the EP Will There Be Peace? in 2021, stepping into the deep tradition of heavy metal coming out of the Rio de Janeiro satellite cities. The project sits firmly in classic heavy metal territory, prioritizing melody and traditional song structures over extremity.

Masturbation with the Bible is a brutal death metal and goregrind band from Caracas, Venezuela, active since 2013. They released their debut full-length "Drowned in Holy Vaginal Fluids" in 2018 through Narcoleptica Productions, followed by the compilation track "Good Nuns Gone Dirty" and the 2025 album "Odium," recorded at Masacre Studio. Their material deals in blasphemous, anti-religious, and extreme gore imagery delivered through a relentlessly heavy slamming brutal death framework.

Masturbator is a death metal band from Franca originally active from 1987 through the mid-1990s, with a 2010 reformation bringing the band back to life. Their 1992 demo 'The Pornographic Terror' documents their early raw death metal approach, and the current lineup — built around vocalist Samuel Death Tormentor, guitarist Sidinei Slaughterman, and bassist Jason Dissector — carries forward the same uncompromising brutality.

Mata Borrão emerged from Belo Horizonte's extreme metal underground as a side project of members from Death Dealer and later Putrifocinctor, delivering a chaotic blend of grindcore and death metal with lyrics targeting social inequality, religious fanaticism, and political alienation. Their 2014 album 'Assim Já Dizia Augusto dos Anjos' — recorded at Studio Attack in Belo Horizonte — stands as their defining statement, with the lineup of Igor Gabriel on vocals, Leandro Alves on guitars, Vitor Malta on bass, and Thiago Pena on drums.

Matahero is a crossover and thrashcore band from Santiago, Chile, formed in 2003. The band has built a steady discography over more than a decade, including their self-titled debut album in 2008, the EP Idealismo Inoperante in 2011, and the full-length Pensamiento Lateral in 2015 via Malaidea Discos.

Matakabra brought a confrontational edge to northeastern Brazil's extreme metal scene, combining deathcore heaviness with death metal, black metal, and djent elements into a sound driven by deeply political Portuguese-language lyrics. Their 2017 EP 'Marginal' — featuring the tracks 'No Açoite' and 'Mordaça' — addressed racism and systemic oppression head-on, earning the band a place in the Força Metal BR annual compilation and a performance at the long-running Abril Pro Rock festival in Recife.

Matarte is a three-piece metal band from Punta Alta, Buenos Aires, Argentina, formed around 2013, consisting of vocalist Ulises Kaliléc, guitarist/bassist Jonathan Bazan, and drummer Agnatne Ajeivut. The band released their album "Sangra Maldad Eterna" on June 6, 2020, a ten-track record recorded, mixed, and mastered at Tumumu Untungu Home Studio in Punta Alta. Their sound blends melodic death and thrash metal with occult lyrical themes, as heard on tracks like "Dioses Muertos" and "Sacrificio Infernal".

Mate Cosido was a groove metal band from Buenos Aires, Argentina, whose lineup featured vocalist Lito Pared, guitarists Alejandro Venneri and Román Montesi, bassist Gerardo Lucero, and drummer Javier Dorado, who had previously played with Argentine metal legends A.N.I.M.A.L. The band released their self-titled album through EMI in 1996, recorded in June and July of that year and produced alongside Augusto Milharcic. The 12-track record remains their only known release before the band split up.