Looting chests and other ancient storage containers will often reveal some kind of ancient items. These can range from things like keys, or chimes as they are referred to in the game, to some technological items that are from the old world but are no longer things you can use directly.
These items are given to you quite frequently and are sometimes given to you as the main reward for completing some side quests and world events. The question you might have at this point is what are these ancient items used for? Why does the game treat them as though they are rare and valuable items, can they be used for anything?
Do You Need Ancient Items For Anything Important?
It does not appear that there is any important use for the ancient items in this game. I have obviously not completed every single quest and activity but I held onto everything and I never came across a use for them.
There was a message in a loading screen that confirms that there is no direct use for the ancient items in the game.
Are Ancient Items Used For Anything Other Than Selling?
The hard thing with games like this is you could go to a vendor and sell a bunch of these items only to find that when you get much further in the game, these items are used to craft some advanced upgrades and are worth more than their value to the vendor you sold the items to. IS this the case in Horizon: Forbidden West?
A loading screen that appeared during the game will give you a very clear answer to this question. The items are used for nothing more than selling for metal shards.
I can also confirm, having beaten the game, that there is no use for these ancient items. Since I never had a need for the metal shards, I decided to hold onto all of these ancient items until the very end of the game. I did not find myself needing to use them, so this backs up what the loading screen message says. There is no use for the ancient items in this game outside of selling them.