Last Night's Parties: Seth Rogan & Zac Efron Premiere "Neighbors," Jessica Biel Celebrates Tiffany & Co. & More!

When: Thursday, May 1 Where: Shrine Auditorium Who was there: Guests included Lady Gaga, Rihanna, Katy Perry, Steven Tyler, Imagine Dragons, Chris Martin, Lorde, Mel B, Ashley Greene, Lil Jon, Jason Ritter, Hilary Duff, Joe Manganiello, Chester Bennington, Sean 'Diddy' Combs, Juanes, Bobby Bones, Juicy J, Gwen Stefani, Jennifer Lopez, Ryan Seacrest, Selena Gomez, Blake Shelton, Kendrick Lamar, Pharrell, Pitbull, Shakira, Thirty Seconds to Mars, Ariana Grande, Luke Bryan, Arcade Fire, Ed Sheeran, Pitbull, Bastille and Usher. Other details:he first-ever iHeartRadio Music Awards brought together the biggest names in entertainment to Los Angeles to celebrate all things music. The innovative all-new awards show presented by Clear Channel Media Broadcast live on NBC, and on Clear Channel radio stations nationwide and the iHeartRadio digital music platform, Los Angeles lit up as the music of the iHeartRadio app came to life at the inaugural iHeartRadio Music Awards. The show featured performances by recording stars Blake Shelton, Kendrick Lamar, Pharrell, Pitbull, Shakira, Thirty Seconds to Mars, Ariana Grande, Luke Bryan, Arcade Fire, Ed Sheeran, Pitbull, Bastille and Usher – in a world premiere performance of the new Michael Jackson song “Love Never Felt So Good.”and Entertainment paid homage to the City of Angels at the historic Shrine Auditorium on Thursday, May 1. [Rihanna, Ryan Seacrest, Jennifer Lopez] [Selena Gomez] [Jared Leto] [Photos courtesy of iHeartRadio]