Most furniture pieces are made of multiple materials. While the exterior and seating part may be the focal point the foundation of the piece is the frame. The frame is usually not seen when looking at the furniture, but it’s what provides structure to the piece. If you are looking for a lightweight piece an aluminum frame is best versus a steel frame which tends to be heavier. Think about your weather and if you will be moving the furniture frequently, etc. when selecting a frame material right for you.