This guide will let you know what the glowing butterflies do In LEGO Fortnite. It will also show you how to obtain the secret loot.
The glowing butterflies occur pretty randomly in the game. If you find one, you have to follow them and they will lead you to a lootable location.
So make sure that you are prepared for a bit of a track because they will make you run around the map. You will end up getting some good loot and extra resources.