It’s hard to believe it’s been 13 years since 9/11 attacks. Everyone remembers where they were on Sept. 11, 2001, and every year we remember and pay respects to all who were affected by the tragedies that struck New York City, the Pentagon and United Airlines Flight 93.

Many rockers took to Twitter today to remember one of the darkest days in American history. Nikki Sixx, Shinedown, David Draiman, Papa Roach, Motorhead, Dave Mustaine and more remind us to never forget.