AceShowbiz -

Behati Prinsloo shows to the world why she's a lucky woman. The 24-year-old runway model posts an Instagram picture of her fiance Adam Levine nearly naked. The Maroon 5 lead singer shows off his toned hot bod as he strips down to his underwear.

Levine, 34, struts his stuff in what looks like a backstage wearing only black briefs and sunglasses. "70's porn called," Prinsloo captions. "It wants its vibe back. Immediately." The snapshot is approved by many of her followers with one writing, "Sweet mother."

Levine has no problem of taking his clothes off. "I spend most of my life naked," he once said. "In fact, I often have to be told by the people around me that it's inappropriate to be as naked as I am. But I live in California, where it's always warm, so why not?"

He proposed to Prinsloo in July, shortly after they reunited following a split earlier in the year. "It was a surprise," the bride-to-be recalled to Us Weekly. "It hasn't even sunk in yet! Last night, I forgot I slept with my ring on. I woke up and went, 'Oh, hello!' "