The singer had never kissed a woman onscreen before and just thought he'd smooch his romantic interest like he would a girlfriend.
"I didn't know what a movie kiss was," Adam told SiriusXM radio host Howard Stern. "I wouldn't say I jammed my tongue down her throat but I would say I gave her a real French kiss. I'll never forget it as long as I live."
"I go in to kiss her and she's like, 'Whoa! Whoa! Whoa! Whoa! Whoa! Whoa cowboy...!' I was like 'What did I do?' She's like, 'You don't use the tongue.' "
Kelly then taught Adam all about the etiquette of the perfect screen kiss, and their smooch became iconic.
"It was one of those isolated, beautiful experiences," he added. "The video wound up becoming this classic video that everyone loves. I never got to speak to her about it. Life goes on and obviously, we never crossed paths again."
Preston, who was married to John Travolta, lost her secret battle with breast cancer in July (20) and Levine is still stunned the "Jerry Maguire" star is dead. "It's so crazy that she passed away," Levine said. "It blows me away. I can't even believe it."