Lady Gaga Owns Lollapalooza's Main Stage

There were plenty of excellent highlights on Lollapalooza 2010's first day, including an amazing display of genre-bending by B.o.B, a stellar showing from New Pornographers, a sharp headlining set from the Strokes and an impressive we-can-still-go performance from Devo. But there was one artist who could truly call herself the Queen of Lollapalooza, the type of performer who managed to permeate every festival-goer's mind and attitude all day long. Not only did Lady Gaga deliver an unbelievably energetic, passionate, hard-hitting set of her own, but she also dropped in on friends Semi Precious Weapons to bang on the drums, sing backup, make out with singer Justin Tranter and do a full-on stage dive into a sea of humanity.

Of course, it was her own set that turned the whole day up to 11. Gaga brought a scaled-down version of her Monster Ball tour to Grant Park in Chicago, and though some of the narrative elements were missing, she still delivered an action-packed two hours of body-popping disco, flashy glam and hands-in-the-air pop. She also hit all of her usual costume changes, including her "disco bra," her monster claw and this purple outfit.

(Click here for all the best photos from the first day of Lollapalooza, including Lady Gaga, Semi Precious Weapons, Devo and more!)

Saturday (August 7) promises high-profile sets from Green Day, Phoenix, Spoon, AFI and dozens of others. Be sure to watch "Lollapalooza Live" at 5 p.m. Eastern and stay tuned to MTV News and the MTV Newsroom Blog for all your Lollapalooza needs.