Sandwich panel, consisting of two layers of formed metal panels (or other material panels) and a polymer insulation core directly foamed and matured in the middle of the panels, is easy to install, lightweight, and efficient. The filling system also uses a closed bubble molecular structure, which can prevent the condensation of water vapor. Sandwich panel is a common product in current building materials, which not only has good flame retardancy and sound insulation, but also is environmentally friendly and efficient. A sandwich panel enclosure is a wall made of sandwich panels.