The Rock in Rio Madrid 2010 festival is developing into the most rock of the eight RiR festivals since the inaugural version in 1985 in Rio de Janeiro.

RiR Madrid organizers today (Feb. 24) added veteran rock band Motorhead and Madrid rock group Sober to the bill. They will join U.S. heavy metal stalwarts Metallica on the festival's final day, June 14.

Tickets went on sale on Feb. 23 at the central Madrid El Corte Ingles department store, which is one of the festival sponsors. Many fans slept outside the store in the street before it opened at 10am, and by 4pm more than 32,000 tickets had been sold at €69 ($93).

Madrid's 2008 festival was attended by 290,000 people.

Rock in Rio Madrid 2010 will be staged over two weekends in June, following a two-weekend Rock in Rio Lisbon festival in Portugal. The Madrid event will again be held at the Rock City in Arganda del Rey, 17km outside Madrid.

Artists include Bon Jovi and John Mayer on June 4; Shakira, Rihanna and Calle 13 on June 5; Miley Cyrus on June 6; Rage Against The Machine on June 11; and Sober, Motorhead and Metallica on June 14.

The festivals are organized by Brazilian founder Roberto Medina, who plans to take Rock in Rio to other global cities, especially in Asia.