Songfacts®:

• "Fireflies" brings together Martin Garrix and U2, combining Garrix' bright, festival-sized electronic production and the Irish band's trademark anthemic sweep. It is the sort of collaboration that sounds designed for a summer night when everyone is holding a phone above their head and nobody has quite remembered to check the time.
• The title is a metaphor for two people whose connection creates its own light. The chorus puts the idea plainly:
  
  You and I are fireflies
  Born for the summer skies
  The light that's in each other's eyes
  Fireflies
  
  The result is a romantic, glowing end-of-summer song about finding someone who makes the world seem brighter.
• The song has nothing to do with Owl City's 2009 hit "Fireflies" other than sharing the title and the general concept of things glowing in the dark. Owl City's song is a dreamy, insomnia-fuelled synth-pop reverie, while Garrix and U2 use the same word as the image for a widescreen love song. One is about lying awake at night; the other is about finding someone worth staying awake for. Both involve nocturnal illumination, although only one requires a stadium-sized lighting rig.
• "Fireflies" continues the creative relationship between Garrix and U2 that started when Garrix worked with Bono and The Edge on "We Are The People," the official anthem of the 2020 UEFA European Football Championship. Garrix later produced U2's "Your Song Saved My Life" for the Sing 2 soundtrack and was involved with "Scars" from U2's Easter Lily EP. "Fireflies" is the first time all four band members have played on a Garrix/U2 collaboration.
• The song was first performed live at Tomorrowland on July 17, 2026, with The Edge joining Garrix onstage before its official release a week later. Garrix revealed that "Fireflies" had been in progress for six summers before finally emerging.
  
  The Edge said the live premiere was a rush and that he likes playing outdoors because "there's no ceiling," which fits the song's open-air, stadium-sized mood.