King Bed". Rihanna promoted "California King Bed" with performances in Milan, Paris and Hamburg, because she was appointed ambassador for Nivea skincare. Rihanna opened the Billboard Music Awards on May 22, 2011, performing the remix of "S&M" with Britney Spears at the MGM Grand Garden Arena in Las Vegas. The performance attracted complaints about the overt sexual nature of the broadcast on a publicly owned television channel. Rihanna performed on NBC's Today show on May 27, 2011, as part of a Summer Concert Series. She performed "S&M", "Only Girl (In the World)", "What's My Name?" and "California King Bed". Tour To further promote Loud, Rihanna embarked on her fourth concert tour, the Loud Tour, in June 2011, having announced it on February 9, 2011. The tour comprised 101 show dates, 32 in North America, 1 in Central America, 4 in South America and 64 in Europe. Tickets sold well in the United Kingdom and some additional shows were added. She performed ten shows at London's O2 Arena. Rihanna was interviewed by Ryan Seacrest on American Idol, and talked about the design of the stage, stating: "We've just designed the stage and we have a section that we are building ... where the fans can actually be in the show and in the stage and be closer than they've ever been. It's real VIP." The North American leg of the tour began on June 4, 2011, in Baltimore, United States. Originally, J. Cole and CeeLo Green were planned as supporting acts for the North American leg. However, Green left the tour, citing schedule conflicts. Rappers Drake, Kanye West and Jay-Z made guest appearances on some dates to perform their collaborations "What's My Name?", "Run This Town", "All of the Lights" and "Umbrella", respectively. The tour was received positively by critics, with some calling it "Rihanna's best tour yet". Jane Stevenson of the Toronto Sun commented that "the two-hour, larger-than-life show lived up to the billing." Jon Brean of the Minneapolis "Star Tribune" remarked, "The Barbadian singer is more visually and vocally dynamic than she has ever been before." Critical reception Loud received positive reviews from music critics. At Metacritic, which assigns a normalized rating out of 100 given to reviews from mainstream critics, the album received an average score of 67, based on 22 reviews. Jon Pareles of The New York Times perceived a "hermetic, cool calculation" on the album, writing