It was a chance encounter in 2015 between Marc (guitarist) and Axel (Drums), two strangers who discovers a fraternal friendship and their mutual love for music, especially for Symphonic Metal. As a result, Synmetalium was created in Lausanne in September 2015. Great admirers of the Finnish band Nightwish, they devoted their first tour as a homage to their favorite artists. The setlist includes twelve of the most representative song of their repertoire. They were joined a few months later by Conrad (bass), Sophie (keyboard) and Federico (violin), all from different musical backgrounds which give a very particular sound to the music of Synmetalium.

Synmetalium searched for a charismatic and female singer who can take the center stage. The group found its choice in Julia. The new member wishing to contribute to the elaboration of the setlist, she proposed the band to come back at the beginnig of Nightwish history, by doing a reinterpretation of "Angel Fall First".

Synmelium recorded "Dark Chest of Wonder" in July 2015 and gave their first concert in August 2015.

Then, Synmetalium trew himself a musical challenge: staging a play who mix symphonic metal and theater. That gave birth to "Flo'eah ou la corruption du monde". For this project, they collaborate with the actress Loraine Pernet for the theatral part.

In September 2015, music, costumes and sceneries were presented at the Theater de la Voirie in Pully. For the first of the spectacle, the band decides to found the festival "6 Hours of Symphonia", which took place. During this event, some of their friends are invited to share the stage.