Sirenia was founded in Stavanger, Norway in 2001 by Morten Veland, shortly after his departure from Tristania, a band he had co-founded. Veland brought an early batch of compositions with him and used them to build the debut album At Sixes and Sevens, establishing the band's template of gothic metal layered with symphonic orchestration, soprano vocals, choral arrangements, and Veland's own death growls. The band has released twelve studio albums over more than two decades, with Veland handling nearly all instrumental duties throughout. Sirenia remain one of the most consistent acts in European symphonic gothic metal.

Sirens of Crisis blend crust and sludge metal from Leverkusen, combining punk's raw urgency with sludge's crushing weight. Active since 2014, they bring a politically charged, abrasive sound to the Rhineland heavy scene.

Cork's Sirocco blend folk and heavy metal with a name referencing the hot Mediterranean wind since 2020. Their incorporation of traditional elements into metal reflects Ireland's rich folk music heritage.

Sisko play thrash metal from Frankfurt, channeling old-school velocity and aggression from the Hessian financial capital. Active since 2016, they represent the ongoing vitality of thrash in one of Germany's major cities.

Sister formed in Jönköping, Sweden in 2006, building a hard-edged sleaze rock sound that drew equally from 1970s punk and 1980s Hollywood glam metal. The band signed with Metal Blade Records and released their debut album Hated in 2011, followed by Disguised Vultures in 2014. Described by critics as occupying a space between The Misfits and Guns N' Roses, Sister cultivated a raw, street-level aesthetic at odds with the more polished Swedish sleaze contemporaries. The band later released Vengeance Ignited independently in 2021 and returned with The Way We Fall in 2025.

Sisters of Suffocation is an all-female death metal band from Eindhoven, Netherlands, founded in 2014 by vocalist Els Prins and guitarist Simone van Straten with the explicit goal of building a women-fronted extreme metal act. The band released their debut EP Brutal Queen independently in 2016, followed by their full-length Anthology of Curiosities (2017) and Humans Are Broken (2019) on Napalm Records. Their straightforward death metal approach, free of novelty or genre dilution, earned them performances at major European festivals alongside recognition as one of the more authentic acts to emerge from the Dutch extreme metal underground in the 2010s.

Sisyfos deal in death metal from the Arctic city of Rovaniemi, their mythological name (the man condemned to roll a boulder eternally) reflecting the relentless, repetitive crushing of their sound. Formed in 2019, they bring Sisyphean extremity to Lapland.

Death metal/hardcore crossover band from Zonhoven in Belgian Limburg, formed in 2023. Their fusion of death metal brutality and hardcore aggression creates a punishing hybrid rooted in the extreme underground of the Flemish countryside.

Galway's Six Down have been dealing in sludge metal since 2000, making them one of Ireland's longest-running heavy acts. A quarter-century from the west coast has forged a sound of oceanic weight and relentless undertow.