Mastiff is a doom/sludge metal/hardcore band from Kingston upon Hull, England, formed in 2014. They channel crushing sludge-doom through abrasive riffs and oppressive weight.

Mater Tenebrarum is an atmospheric gothic and doom metal project from Barcelona, Spain, formed in 2020, created by singer-songwriter Lady Morte of Trobar de Morte. The project features female lyrical voices over doom gothic metal compositions, channeling dark, cinematic atmospheres.

Mater Thallium is a doom metal and progressive rock act from Trondheim, active since 2013. The band blends the crushing weight of doom with the exploratory spirit of progressive rock from Norway's third-largest city.

Materia Muerta is a sludge and doom metal band from Patras, Greece, formed in 2025. Their Spanish name meaning "dead matter" captures the crushing weight of their sludge-doom.

Mathan are an epic doom metal band from Vienna, Austria, playing in the traditional doom mold with a focus on slow, heavy riffing and epic song structures. The band has been a fixture of the Viennese doom scene, performing at the Austrian Doom Metal Festival 'Doom over Vienna' alongside other regional and international acts. They remain unsigned and independent, releasing music through their Bandcamp page.

Mathians is a sludge/doom metal band from Novara, Italy, formed in 2020. They channel crushing sludge-doom through abrasive riffs and oppressive weight.

Mathusalem is a band from Paris, France, formed in 2022, having evolved from stoner and doom metal into synthwave. Their stylistic transformation reflects an adventurous creative spirit unbound by genre conventions.

Matote is a stoner, doom, and post-metal band from Badalona, Spain, formed in 2018. They merge stoner metal's fuzzy heaviness with doom's crushing weight and post-metal's atmospheric dynamics.

Matraque is a sludge, death, and doom metal band from Minsk, Belarus, formed in 2013 that grinds through low-tuned, punishing heaviness. Their approach layers crushing sludge grooves with death-doom weight, carving out a suffocating sonic space within the Belarusian underground.