Jackknife Seizure is a progressive metal band from London blending grunge, progressive, and hard rock influences into a distinctive heavy sound. Described as the love-child of Mastodon and The Doors, their albums Starfisher (2017) and Time of The Trilobites feature eccentric vocals, space-themed lyrics, and complex progressive riffs.

Jacobs Moor is a progressive power/thrash metal band from Vienna, Austria, formed in 2014. They have released several albums including Anthems For The Apocalypse and All That Starts, blending technical proficiency with aggressive thrash energy and progressive structures.

Jaggernaut is a heavy metal band from Sweden whose dark, aggressive compositions channel the intensity of the Swedish extreme metal tradition. Their extensive discography including Immortal and Distorted Heavens demonstrates a prolific approach to heavy, uncompromising metal.

Jakub Dukowski is a progressive heavy metal solo artist from Bytom, Poland, whose debut album Beginning Of The Road (2022) features eleven tracks of complex, extended metal compositions. His progressive approach to heavy metal incorporates intricate arrangements characteristic of the genre's most ambitious practitioners.

Janissary is a heavy metal band from Serbia named after the elite Ottoman military corps, delivering aggressive compositions with historical and martial themes. Their approach to metal draws on Eastern European traditions to create a distinctive, powerful sound within the Balkan metal scene.

Jara is a heavy metal band from Germany whose dark, atmospheric approach to the genre draws on gothic and doom influences. Their brooding compositions and heavy sonic textures set them apart within the diverse German metal landscape.

Jarun is a black metal band from Krakow, Poland, blending progressive and folk elements into a distinctive style that sounds entirely their own. Their four albums from Wziemiozstapienie (2012) through Rok spokojnego slonca (2021) feature acoustic flourishes, progressive songwriting, and ferocious vocals, earning praise as a top-tier black metal act.

Javelin is a metal duo from Germany that delivers intense, stripped-down heavy music with a focus on powerful guitar interplay. Their lean lineup allows for a tight, focused approach to aggressive metal that emphasizes riff craft and dynamic songwriting.

Jechane is a Polish metal band from Tuczno whose debut album War in Your Head (2016) delivers thrash, death, and progressive metal with heavy growl vocals and thrashy guitars. Recorded at Szafa Records Studio, the album features thirteen tracks exploring themes of mental conflict and psychological darkness.