It depends how badly shit hits the fan. If it’s just in the US, silver would be something that we have that still has value to the rest of the world. If shit hits the fan worldwide and we’re living off the land, metals wouldn’t be a medium of exchange until we were doing more than just trying not to die. People would barter first, but a medium of exchange is eventually needed. You grow wheat and your neighbor who thinks his dick is going to fly off if he eats gluten happens to be the guy with the cows who produce milk. You could really use some milk for your cereal you make with your wheat, but wheat is your trade and the milk dude doesn’t want it. You’d have to trade some of your wheat with the dude who grows potatoes just to get something that the dude with the milk wants, so in a couple days you trek over to the potato guys farm and trade him some wheat for his potatoes, then you go back to the dairy farm only to find out that the gluten free milk guy ended up getting a sack of potatoes yesterday and doesn’t need any anymore. Now you’re left sitting there thirsty as fuck eating some potatoes with your cereal instead of milk.

See? What a pain in the ass to go through just because you wanted some goddamn milk for your cereal. If only there was something that everyone wanted because it was a means to get anything that they want... something has to fill that role, and it’s been precious metals for millennia. They’re a tried and true currency so it makes sense that people would go back to it.