Steel doors are durable, secure, and weather-resistant entry points, typically made from a galvanized steel skin over a solid core (such as polyurethane or polystyrene) or a hollow steel frame filled with insulation. Key features include excellent thermal and acoustic insulation, high resistance to mechanical damage and environmental factors like extreme temperatures and fire, and robust security against forced entry. They are used in a variety of applications, from homes to commercial and industrial buildings, and are available in many styles, finishes, and with various hardware options.