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.

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.