Fuckjar is a sludge metal band from London, active since 2015 and delivering grimy, punishing sludge from the English capital. The project channels London's grit into unrelenting heaviness.

Fudge Tunnel is a sludge/groove metal band from Nottingham with alternative and noise rock influences, whose 1994 album The Complicated Futility of Ignorance on Earache Records exemplifies their wildly noisy yet catchy approach. The band has been a fixture of Nottingham's heavy music scene since 1991.

Fulci Nightmare is a sludge metal and hardcore band from Kent, England, active since 2012 and named in homage to Italian horror director Lucio Fulci. The project blends sludge metal's crushing weight with hardcore punk's directness.

Fume is a sludge/death metal band from Coventry, England, active since 2018 and merging sludge metal's oppressive weight with death metal's ferocity. The project channels the industrial heritage of Coventry into extreme metal.

Funeral Boogie is a sludge metal band from Lecce in Puglia, formed in 2017. Their name juxtaposes funereal weight with groove-based movement, capturing the paradox at the heart of their sludge metal — music that is simultaneously crushing and rhythmically compelling.

Funeral Hag is a sludge/doom metal band from Brighton on England's south coast, whose 2011 demo features Jon and Nev on guitars, Steve on bass, George on drums, and Monty on vocals delivering tracks like Scorched Planet and Toil (The Grind). The band trades in heavy, slow-trudging doom and sludge in the tradition of Eagle Twin and Thou.

Funeral Smoke is a doom/sludge metal band from Moscow, Russia, formed in 2016. They deliver the heavy, slow-burning weight of doom and sludge metal, their name evoking the acrid haze of cremation.

Funeralboys is a blackened doom/sludge metal band from Ilawa in the Warmia-Masuria lakeland of northeastern Poland, formed in 2024. They blend the crushing weight of doom and sludge with blackened atmospherics from one of Poland's most scenic but musically remote regions.

Furuvgerendufuroval is a black/sludge metal project from Uzhhorod in the far western Transcarpathian region of Ukraine, formed in 2021. Their deliberately unpronounceable name and border-region origins — Uzhhorod sits at the junction of Ukraine, Slovakia, and Hungary — signal the unconventional character of their genre-blending extreme metal.