Moreno entered the stage after the band thrashed through Mezmerize cut "Cigaro." Moreno and System of a Down's lead singer Serj Tankian took turns on vocals, with the Deftones frontman adding his personal touch by letting out a gritty scream on the choruses.
In the middle of the song, guitarist Daron Malakian commanded the massive audience to form multiple mosh pits. "Everybody spinnin' around," he sang as he waited for the fans to form the pits. The crowd moved to the sound of his impromptu song before picking up the pace as the song resumed. After Moreno left the stage, the band took it even further back with 1998 single "Sugar" off their self-titled debut for their headlining set's finale.
System of a Down played the festival on its fourth of seven days. Queens of the Stone Age, Lamb of God and Deftones were among the heavy acts to perform at the popular, diverse show. The sixth installment of Rock in Rio also features Rod Stewart, Rihanna and Katy Perry prominently on its lineup.
In 2006, System of a Down went on hiatus following the release of 2005 double album Mezmerize/Hypnotize. They reunited to play a string of European dates in 2011 and have been touring and headlining festivals ever since. Their 2014 Wake Up the Souls tour commemorated the 100-year anniversary of the Armenian Genocide.