Orgasmo de Porco bring the chaotic spirit of 1980s American crossover to a distinctly Brazilian underground setting, with Caverna's barked vocals riding atop the palm-muted thrashing of Paulinho and the locked-in rhythm section of Lobo and De Cia. Their 2013 debut "My Mind is a Mess" established their irreverent, full-throttle approach, and 2018's "Voltamos mijados e putos" — later named a Bandcamp Album of the Day — proved they only got tighter with time. Released through Läjä Records and Cianeto Discos, their records sit comfortably alongside classic D.R.I. and Municipal Waste without ever sounding derivative.

Orgia Nuclear cook up a volatile mix of speed metal ferocity, thrash riffing, and black-crust grime, having honed their sound from the early "Caos Total" EP (2013) through to the full-length "Desgastado" (2018), recorded at Darkside Studio in Recife. Sung entirely in Portuguese, their lyrics take aim at social and political targets while the music charges forward with metalpunk urgency. Their split releases and active underground presence reflect a band more interested in raw energy than studio polish.

A duo of Sodomizer and Sancta Fêmea, Orgiastic Perversion channel raw and depressive black metal into an uncompromising catalog of transgressive imagery and suffocating atmosphere. Their output spans from the debut "Ritual de Luxúria Sob a Luz da Lua Cheia" (2015) through "Ninfomaníacas e Sádicas" (2020) and "Obsessiva Volúpia da Transgressão" (2022), each release sinking deeper into themes of desire, darkness, and anti-cosmic philosophy. The dense, lo-fi production is entirely intentional — a wall of noise that feels less recorded than summoned.

Orgonite is the solo project of Théo "Desgraçócrates" Luna-Marques, a one-man endeavor where blackened riffing meets traditional heavy metal structure in a grim but melodically aware package. The debut "Caos Interior," released through Gigachad Records, handles composition, performance, and artwork entirely in-house, establishing a distinctive DIY identity in the blackened heavy metal underground. The project draws from first-wave black metal and occult heavy metal equally, refusing to settle in either camp.

Orgullo Fisura is a heavy punk band from Buenos Aires, Argentina, who fuse traditional heavy metal with punk aggression and socially charged lyrics rooted in underground resistance culture. They released "El infierno del heavy punk" in 2015 on Desatan Records, followed by "Derribando muros" on the same label in October 2018. The band has been a consistent presence in the Buenos Aires underground scene, with a catalog that also includes earlier releases such as "HeavyPunk de carretera" (2017).

Orion were founded at the end of 2001 in San Javier, a town in Chile's Maule region, with the stated aim of channeling the spirit of 1980s thrash and death metal. The band released their debut full-length Mysterivm Cosmographicvm in September 2020 through Iron Blood and Death Corporation, recorded and mastered at Equinox Studios in Rancagua, weaving philosophical and ancient-world themes through nine tracks of old-school death/thrash.

Orizzon bring a four-piece lineup — vocalist Tiago Pierucci, guitarist Marcos Duran, bassist Leonardo Gonçalves, and drummer Fabricio Mendonça — to a sound that fuses classic heavy metal muscle with progressive songwriting ambition. Their 2024 debut "Inner" confirmed the band's intent to bridge old-school power and modern technical sensibility without defaulting to either extreme. The result is a progressive metal record that values memorable hooks alongside compositional depth.

A solo project by multi-instrumentalist Danilo Rakkaus, Ormsdóttir debuted in early 2024 with the three-song EP Children of Sin, drawing from classic Black Sabbath-style doom while threading in stoner and depressive textures. The tracks range from driving, energetic riffs to slow, heavy passages, making a compelling first statement for a one-person outfit with a clear ear for contrasting moods.

Orthostat play a dense, riff-heavy style of death metal with an ear for odd time signatures and shifting dynamics, from doom-laden crawls to blastbeat surges. The band's 2019 debut full-length Monolith of Time, recorded at Hell Frost Studio by vocalist-guitarist David Lago, weaves its themes of ancient civilizations and cosmic scale into an album that reviewers praised for being unusually memorable within the old-school death metal field.