Why do we care about music festivals? Maybe that question can be better answered by seeing the magnitude of festival news this week.  In Rio, Metallica and The Red Hot Chili Peppers are confirmed to headline next September’s Rock in Rio festival. Across the pond, Kings of Leon and Foo Fighters have been announced as headliners for Isle of Wight 2011. And in perhaps the biggest news of the week, the Barcelona-based Primavera Sound dropped another indie-tastic batch of confirmed artists, including Belle & Sebastian, Animal Collective, The National, Fleet Foxes, and The Flaming Lips.

As for the U.S.? Well, both Bonnaroo and the Ultra Music Festival announced their 2011 dates and The Rolling Stones are rumored for Coachella. Oh, and CMJ already wants us to start planning for next October. So, yeah, this is why we care about music festivals.

Below, we have a recap of all this week’s news and rumors. Also, don’t forget to bookmark Festival Outlook and/or follow us on Twitter. That way you won’t have to wait until Wednesday before getting your festival fix.

News:

– The Barcelona-based Primavera Sound added more acts to its 2011 lineup, including of Belle and Sebastian, Fleet Foxes, The National, The Flaming, Lips, and Animal Collective, among others.

– Metallica, The Red Hot Chili Peppers, and Snow Patrol will headline Rock In Rio 2011, with even more big names to be announced.

– Kings of Leon, Foo Fighters, and Pulp are three of the acts confirmed for this year’s Isle of Wight.

– Godspeed You! Black Emperor, Fuck Buttons, and Boris are among those set to play the first-ever I’ll Be Your Mirror festival in Japan next February.

– The Miami-based Winter Music Conference and Ultra Music Festival announced their 2011 dates. So did Bonnaroo. CMJ, too.

Lineup Additions

– Coachella: The Rolling Stones, Wire (Rumored)

– Bonnaroo: 2011 dates announced; Portugal. The Man (Expected)

– Primavera Sound (Spain): Added Animal Collective, Belle and Sebastian, Fleet Foxes, The Flaming Lips, John Cale performing Paris 1919, The National, Mogwai, Swans, and Suicide

– Ultra Music Festival: 2011 dates announced; Crystal Castles, Erick Morillo, Jose Nunez & Harry Romero (Expected), Girl Talk (Rumored)

– Rock Am Ring (Germany): Kings of Leon confirmed as first headliner

– Rock in Rio (Brazil): Red Hot Chili Peppers, Metallica, and Snow Patrol confirmed as headliners

– Isle of Wight (UK): Foo Fighters, Kings of Leon confirmed as headliners

– ATP’s I’ll Be Your Mirror (Japan): Official lineup includes Godspeed You! Black Emporer, Autolux, Boredoms, Boris, Dirty Three, Envy, Fuck Buttons, and Melt Banana

– Lollapalooza: Portugal. The Man (Expected)

– Glastonbury (UK): The Coral (Rumored)

– Sweden Rock Festival (Sweden): Added Styx, Mason Ruffner.

– Freezing Man Festival: Official lineup includes Broken Social Scene, Chromeo, Major Lazer, Shout Out Out Out, and Stars

– Brooklyn Electronic Music Festival: Official lineup includes Brahams, Javelin, Kid Sister, and more

– CMJ Music Marathon: 2011 Dates announced.

– Melt! Festival (Germany): 2011 dates announced