Metalbirds are laser cut from Premium 1/8 inch Corten steel.A copper chromium alloy steel, our premium Corten steel is weather resistant - it's designed to quickly develop a patina (commonly assumed to be rust), which then gives a layer of protection sealing in the steel and preserving it. It means that Metalbirds last for decades, with a patina that changes with the seasons. Corten is the steel you see used in high-end exterior architecture. Once it develops a patina, it looks beautiful for years.