Why does metal need a protective coat on it?

Metal needs a protective coat to prevent corrosion and degradation caused by environmental factors such as moisture, oxygen, and chemicals. Without a protective layer, metals like iron and steel can rust, leading to structural weakness and shorter lifespan. Coatings, such as paint or galvanization, act as barriers that shield the metal surface, extending its durability and maintaining its appearance. Additionally, protective coatings can enhance resistance to scratches and impacts.