Monsters of Rock '91 is a hard rock/heavy metal tour festival that American heavy metal band Metallica played on, it would be their fourth time on the tour. Like the last time Metallica played on the festival it would feature the live debuts of songs of their upcoming album, this case being Enter Sandman and Sad But True off 1991's Black Album. It would also feature the band's first concert in Russia, famously taped on A Year and a Half in the Life of Metallica.