You probably don't think much about tin cans, even when you're buying one. It's the product inside the can—soup, beans, maybe hairspray or sunscreen—that seems to matter.
But the humble tin can is both a crucial component of modern, globe-spanning supply chains and a product of them: About half of the metal used to make tin cans in the U.S. is imported from abroad. And that's why tin cans—more specifically, tinplate steel, the type of metal used to make those cans—are at the center of a behind-the-scenes fight over tariffs that illustrates so many of the problems with protectionist policies.
