Michael J. Fox Takes Glastonbury Stage w/ Coldplay ... 'Fix You/Johnny B. Goode'
Michael J. Fox can still shred on the guitar ... taking the stage alongside Chris Martin and Coldplay -- and playing a mashup "Back to the Future" fans know so well.
The actor took the stage at the Glastonbury Music Festival in England Saturday night during the band's headlining set ... and, ya gotta watch the video 'cause it's a tear-jerking tribute to the film and TV legend.
The vid kicks off with Chris and the crew jumping into their hit song "Fix You" -- Michael's already onstage, sitting in a wheelchair and holding a guitar on his lap.