2D lattice metamaterials composed of beams or rods are widely used in different technical fields. An important feature of such materials is that, through structural design of the unit cells, they can exhibit many unique mechanical behaviors that traditional materials do not have. In this review, recent advances in the study of bending deformation of lattice metamaterials are briefly summarized, with emphasis on the unconventional bending modes and dominant mechanisms, as well as the corresponding theoretical models of the continuum. The main problems and challenges in future research are also prospected.