MAROON 5 was performing in Anaheim on Monday, when a female fan couldn't repress her desires any longer . . . and stormed the stage to give ADAM LEVINE a big hug. She came from behind him, so he was taken by surprise. He grappled with her for a bit, then put his arm around her, before security came in and escorted her away. Adam waved goodbye to her . . . kind of sarcastically. He finished the song, shrugged, and said, quote, "That was [effing] weird, right?

"She like, cut my ear with her fingernail . . . it's just weird to be, like, in the moment, ya know? And then the next thing you know someone's [effing] in your face. It's super terrifying." (Here's video.)