Steel doors are manufactured from strong steel. However, they are not entirely made of solid steel. In fact, a steel door is a polyurethane or polystyrene core coated with a thin skin of steel material. They are commonly used for industrial and commercial purposes. It lasts longer, requires the fewest repairs, and is sturdier than other products. Steel's natural strength also outperforms other materials in security, fire rating, sound reduction, vandal resistance, sanitation, and more. Hollow metal will outperform wood, aluminum, and fiberglass in demanding environments.