Machine Gun Kelly Apologizes for Shoving Stagehand During Concert

Machine Gun Kelly seemed quite pissed during one of his concerts after his guitar wasn't working, and he took it out on one of his stagehands ... for which he's now apologized.

The Cleveland rapper was performing Friday night at the Credit Union 1 Pavilion in Chicago, where at one point while he and his band were rocking out to MGK's "Hollywood Whore" ... an equipment malfunction occurred, and Kelly kinda lost his s*** up there.

TMZ got video of the meltdown moment, where MGK realizes his guitar isn't working at a part of the song where it's supposed to (his guitar solo, it seems), and he rushes over to the backstage area to see what's going on ... confronting a frantic stagehand.

He seems to make some sort of physical contact with the guy before rushing back to the other side of the stage, with the stagehand following close behind with a mic stand.

Once they're on the left side again, Machine Gun Kelly appears to shove his guitar into the stagehand's chest, clearly frustrated with him as the guy scurries off back to the right again.

The song continues to play as MGK awkwardly stands in the back, not having played a lick of guitar through most of the ending of the track ... and things ended even more poorly as Kelly appeared to lurk over to the stagehand who appeared upset and flustered.

MGK climbs a box behind the main stage and stares the dude down from above, and then LEAPS down and follows him back stage as the guy tries to get away. Bad look, right?

Seems like Kelly himself realized just how nasty he'd acted, and took to Twitter after the show to address it. He wrote, "tonight the frustrations from my personal life came out on the stage. sorry to my fans and my band. i’ll get help after tour is over."