One of the Fortnite Chapter 3 Season 4 quests for Week 3 says “Destroy Chrome Structures.” Not only does the game not really explain how to do this, some of the chrome structures you break don’t count towards the quest progression.
Destroying things that start off chrome doesn’t complete the quest, with the exception of ammo boxes, chests, and other loot boxes. You have to use Chrome Splash to turn new structures chrome before you destroy them.
The best way to do this is to throw Chrome Splashes into buildings with lots of things inside. We dropped into Tilted Towers and were able to complete the quest fairly quickly, though some random decoration items (like chairs) don’t count towards the 100 chrome structures.
You can find Chrome Splash in chests, but you can get it easier if you just break existing chrome structures. Randomly, breaking these structures will make a Chrome Splash pop out. That being said, using splash to chrome-ify more structures and breaking those structures rewards more splash, so once you find one, you should have an endless source of Chrome Splash.