System Of A Down and Green Day have been named among the 2021 headliners of the German festivals Rock am Ring and Rock im Park.The twin festivals, which are usually held simultaneously, were cancelled for 2020 earlier this year due to the coronavirus outbreak.The organisers of Rock am Ring and Rock im Park have now confirmed that SOAD, Green Day and Volbeat, who were due to headline the festivals this year, will top the bill in 2021.The twin festivals will take place from June 11-13, 2021, with