The phrase "tin cans" refers to small metal containers made from thin sheets of tin that are formed into a cylindrical shape and then sealed shut with solder or another type of adhesive. These containers have been used for centuries to store food, drinks, and other items, due to their durability, affordability, and ease of production. The phrase is often used in a figurative sense to describe something that is easily defeated or overcome, as the term "tin can" has become synonymous with something weak or insignificant.