"My Songs Know What You Did in the Dark (Light Em Up)", also known as simply "Light Em Up", is a song by American rock band Fall Out Boy, released as the lead single for the band's fifth studio album, Save Rock and Roll.[1] It serves as the band's first single following the group's three-year hiatus and regrouping in early 2013.[2] The track and its music video were released on February 4, 2013, worldwide and February 5, 2013, in North America,[3] to coincide with the official news of the band's reformation. The song impacted radio on February 19, 2013.[4] The band members felt that the song best represented their album at its core. The song's title and principal lyric originate from an unrelated 2004 demo by the band.[5][6] Fall Out Boy performed "My Songs Know What You Did in the Dark (Light Em Up)" on Jimmy Kimmel Live! for the group's first post-hiatus TV performance on February 13 as well as on various TV shows throughout the entire year, and have extensively played it in acoustic version at radio interviews. Lead vocalist and guitarist Patrick Stump performed the song as a guest on singer-songwriter Taylor Swift's Red Tour on July 13, 2013, and Swift guested in turn with Fall Out Boy on Victoria's Secret Fashion Show 2013 on November 13, 2013. The song became a staple at several sports-broadcasting soundtracks that year.[7][8] The music video is part one of The Young Blood Chronicles, a series in which a video was eventually recorded for every song on Save Rock and Roll as part of a narrative. "My Songs Know What You Did in the Dark (Light Em Up)" was a comeback success, reaching the two million digital downloads mark in July 2013, being the fourth song by Fall Out Boy to do so, and was certified 3× Platinum by the end of the year. It was named by BBC Radio 1 as one of the "Top 100 Tracks of the Past 5 Years"[9] and No. 1 on Sirius XM Hits 1's best of 2013 countdown.[10] It reached the top 10 on both Pop Songs and Alternative Songs with heavy airplay, and peaked at No. 13 on the Billboard Hot 100 with twelve consecutive weeks in the top 20.[11]