This challenge is part of the Location Domination Overtime Challenges in Fortnite. To complete all the stages of the challenge, you'll have to collect metal at Hydro 16 or Compact Cars. Go to one of these two locations on the map.
Map
Compact Cars is located east of Frenzy Farm while Hydro 16 is south under the dam.
When the challenge comes out, these two places are likely to be assaulted by players. If you want to complete this challenge in peace, wait a little for the game to run its course and go collect the metal after the war. There should be enough left to complete your mission!
Original content by Maxime "Biaggi" Ricoveri.