metal foam has a porosity of more than 90%. The holes are also divided into open cell and closed cell. The metal foam made with the hole is very soft, soundproof, heat conductive, and the energy absorption effect is good. The metal foam rigidity of the closed hole is increased, but its rigidity and toughness are positively correlated with the structure type and density of the pores, and no corresponding experiment can be found to determine its strength. There are related papers on materials science, you can see for yourself that the properties of metal foam made of aluminum, copper and nickel are different.