A steel frame is a skeleton of steel beams and columns that supports a building. The frame carries the loads. The walls, floors, and roof hang off it or rest on it. Steel frames made skyscrapers possible because they are strong, light, and can be erected quickly.

Steel has a high strength-to-weight ratio. A steel beam can span farther than a timber beam of the same weight. Steel columns take up less floor space than concrete columns. Steel can be prefabricated in a shop, shipped to the site, and bolted or welded together. That speed is a major advantage on tight schedules.

Steel has weaknesses. It loses strength at high temperatures, so it must be protected with fireproofing. It can corrode, so it must be painted or galvanized. It can buckle under compression if not braced properly. Connections are critical, especially in seismic zones where the frame must absorb energy without fracturing.

Most tall buildings use steel frames, often in combination with concrete slabs. The frame does the structural work. The facade does the rest.