Sebastian Bach won't embrace his fans with open arms ... literally, it seems 'cause if you ask the guy for a hug, he's going to blow up on ya.

The heavy metal singer was performing Friday night in Las Vegas as part of the 2025 Chevy Metal Summer Tour. Chevy Metal is a Foo Fighters cover band featuring Taylor Hawkins ' son Shane on drums. Getty

Sebastian hopped on the mic for the show ... and, after a song ended, he flipped off a woman in the crowd and started cussing her out.

Check out the clip ... we've bleeped a number of the cuss words -- but, Bach really rips into this woman.

Bach then explains to the audience this fan came up to him and his wife before the show ... and, he claims she asked his wife's permission to hug him. TMZ.com

Sebastian clearly told the woman no

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