Abstract: How to reduce theweight of existing materials and structures without compromisingtheir mechanical properties has been a challenge in front ofmaterials scientists and mechanists. This article presents acomprehensive review on various processing techniques for a noveltype of ultralightweight material -- periodic lattice metallicmaterials -- and on the key welding technique for fabricatinghigh-performance sandwich panels with these cellular materials asthe core. Based on our own researches, various hardeningtechniques are discussed for enhancing the mechanical propertiesof lattice metallic materials.