Metal bread pans can be shiny or dark. Ones made of darker metal produce a darker crust; ones made of light metal, a lighter crust. The metal can be bare, or treated with a non-stick coating.
Professional-grade metal bread pans are made of heavier metal, so that they can stand up to heavy use and banging without denting as easily as home-grade ones would under such intense use. These will also hold the heat well.
Older-style consumer-grade metal bread pans in North American had pleated corners made of tin plate or blued steel. Often the metal was dimpled.
Metal bread pans may stick the first few times you use them, until they get seasoned. Some people swear that the secret to metal bread pans is to season them, and never, ever wash them.
Dry all metal ones well before putting away. Don’t scrub metal ones, and don’t put them in the dishwasher. Just rinse them with warm water and a sponge or cloth. You can use warm water, and soap on non-stick ones.
Metal bread tins didn’t really exist prior to the 1700s. They could in theory have been made of iron, but that was heavy, and expensive. Most bread was risen and baked free-form, particularly in the classic round sourdough shape.
In the 1700s, the tin mines in Cornwall, England, were mined in earnest again for the first time since the Romans, and the tin was used to make affordable bread pans. Bread baked in these bread pans could be toasted and sliced more easily — just in time for the rise in popularity of the sandwich.