Hellfest is a major French festival that was held over the weekend. On Sunday during Voivod's set, the veteran thrash band was joined by Jason Newsted for the song 'Voivod' (watch above) and Phil Anselmo for 'Astronomy Domine' (watch below).

Voivod are back on the road after having to cancel some dates earlier this spring. Frontman Denis 'Snake' Belanger had to undergo a procedure to deal with diverticulitis, which put them on the sidelines for several weeks.

Newsted is a former member of Voivod. He produced and played on their 2003 self-titled album, and also laid down bass for 2006's 'Katorz.' He's currently in the band Newsted, which also played at Hellfest. After an EP earlier this year, Newsted's full-length debut 'Heavy Metal Music' will be unleashed Aug. 6.

Anselmo's band Down also played at Hellfest. The day before he played with Voivod, Anselmo  jumped up on stage with Accept for the song 'Fast as a Shark.' His first solo album 'Walk Through Exits Only' is set to be released July 16.

They are in Europe now, but North American fans of both Newsted and Anselmo will be able to see them live soon. Newsted are part of Gigantour, which kicks off July 3. Anselmo and his band The Illegals embark on the Technicians of Distortion tour July 31.