Thirty Seconds To Mars serenaded James Nieto, the winner of the iHeartRadio Grand Prize Experience package, with an intimate cover of Rihanna's "Stay." The band walked Nieto back to their dressing room where Jared Leto, Shannon Leto and Tomo Miličević all took part in the acoustic rendition.

PHOTOS: Thirty Seconds To Mars perform at the iHeartRadio Music Festival.

VIDEO: Thirty Seconds To Mars cover Rihanna's "Stay" at the iHeartRadio Music Festival.

Frontman Jared Leto ended the cover by saying how he likes to perform a "low quiet version" to warm up his voice before a show. Nieto described the once-in-a-lifetime performance with one simple word, "Incredible!"

Check out a few photos of Nieto and the band below:

Photos: Stephen Eckert for iHeartRadio

*Follow the author, Stephen Eckert, on Twitter @S_Eckert