A$AP Rocky may have the biggest hit of his career on his hands with "Good For You," which has hit at No. 9 on the Billboard Hot 100, just a spot lower than the peak for "F--kin' Problems" -- and it comes with a somewhat unlikely companion: Selena Gomez.

Still, he says the partnership came together with ease.

"They reached out," he told MTV News at Lollapalooza on Sunday. "She said she wanted me to f--k with it."

And so he did f--k with it -- including the beat.

"Me and my boy Hector [Delgado], we added to the beat. We added instruments and sh-t -- more bass, snares. I started singing on it. Produced it. Wrote it."

Though this track differs a bit in sound and content from what fans are used to hearing from Rocky -- he makes eclectic-sounding music, but this is a pop favorite -- he says he didn't change the way he attacked the track from his normal methods.

"I don't think it's a different approach," he explained. "You just go in. Go for the kill. I mean, it wasn't the type of song you try to go into... It was just like me telling her, you sure you wanna go here with me? I gotta change the beat. I gotta talk my sh-t. My jiggy sh-t."