U.S. heavy metal stalwarts Metallica will headline the last day of the five-day Rock in Rio Madrid 2010 festival in Spain, organizers announced today (Feb. 17), just 24 hours after revealing that John Mayer and Puerto Rican reggaeton duo Calle 13 will also play the festival.

Rock in Rio Madrid will be staged at Rock City, a 200,000 square meters area in Arganda del Rey, 17km outside Madrid, over two weekends in June. Artists lined up so far are Mayer and Bon Jovi on the first day, June 4; Shakira, Rihanna and Calle 13 on June 5; Miley Cyrus on June 6; and Metallica on June 14.

Metallica has played several Spanish summer festivals over the years. Its last appearance in Spain was in 2009, during its World Magnetic Tour. The band has sold more than 100 million records, says Rock in Rio, and has received nine Grammy awards.

Mayer's appearance will be his first ever concert in Spain, and will follow the March release of his new album "Battle Studies" (Columbia). Mayer has won seven Grammys since the release of his first album "Room For Squares" in 2001, and he has sold nearly 12.5 million albums since then, says RiR.

The black humor of Calle 13's Rene Perez Joglar, aka the Residente, and Eduardo Jose Cabra Martinez, aka the Visitante, is well known in Spain. The duo won all five Latin Grammys they were nominated for at the 10th Latin Grammy ceremony in Las Vegas.

Rock in Rio was born 25 years ago in Rio de Janeiro in January 1985. Subsequent events in Lisbon and Madrid have been arranged by its Brazilian founder, Roberto Medina. This will be the second Rock in Rio Madrid - the first in 2008 was attended by 290,000 fans.