Flux is one of the most unique and most rare items in Fallout 76 because of when are where you can get it. Flux can only be found after there has been a nuclear strike in the game. Players will need to go into the blast zone after the area has been burned to a crisp to find a plant that is called Flux.
Flux will be used in very rare items and has multiple variations that can be found. Flux will be found in different color variants: Crimson, Cobalt, Violet, Flourescent, and Yellow Cake. Everything that the Flux can make is unknown, but it is a known ingredient in making Fusion Cores.
Once a nuclear strike has been launched in your game, you will need to go into the blast zone to recover this material. Keep an eye out for strange looking plants and you can pick them up like every other item in Fallout 76.
Make sure you put your Flux in a safe spot, like your Stash, so when you the recipe calls for it you’ll have it ready to go.