According to WWE.com, METALLICA's new song "All Nightmare Long" will serve as the theme for the October 5 pay-per-view WWE event No Mercy.No Mercy is an annual professional wrestling pay-per-view event produced by World Wrestling Entertainment (WWE). The first No Mercy was held on May 16, 1999 in Manchester, England. No Mercy is held every year in October and from 2003 to 2006 the event was exclusive to the SmackDown! brand. Although WWE is known to pick mainstream music for their pay-per-view theme songs, No Mercy sometimes features its own WWE-produced theme song entitled (appropriately) "No Mercy". This song was composed by WWE's music producer Jim Johnston. The song debuted at No Mercy 2002 and was featured in full on that event's DVD. The song was later remixed and used again for No Mercy 2004 and again in 2006, also being featured on the event's DVD. The lyrics vary slightly between the two versions. In 2007 the song was remade with different sounding instruments and a different vocalist.