The topic of this paper is alternatives to heavy steel structures, namely aluminum and, above all, composites. Since composites are all materials made of at least two different materials that have different physical and chemical properties, there are several structural divisions, but only one of these is covered in this work. In the introductory part, aluminum is mentioned as the basis of lightweight structures, with special emphasis on a variety of applications and different characteristics that require a different approach to production and maintenance compared to heavy steel structures. In the continuation of lightweight structures, hybrid materials, ie structural composites - sandwich panels, are processed. In this area, the term lightweight construction changes its meaning from light metals to new hybrid nonmetallic materials. Through the presentation of the contents about the sandwich panels, the advantages, the areas of application, the materials and the production are considered. Different usage result in different loads that require individual testing. In the section dealing with the topic of sandwich panels, efficiency is defined by different criteria, with the determination of equivalent values. An interesting payload-to-weight ratio is shown through analytical testing. It is presented how relatively high load-bearing capacity for low-density materials can be achieved, with appropriate geometric parameters. The last section provides examples of cost-effectiveness and flexural stiffness efficiency. Examples are presented by analytical method and in chart form.