The current study introduces a novel class of bio-inspired and 3D-printed metastructures called functionally graded lattice metamaterial beams (FGLBs). These lightweight lattice metastructures offer several benefits, including a high stiffness-to-weight ratio and excellent energy absorption efficiency. Therefore, their mechanical properties reinforced with AL-FRP (fiber-reinforced polymer) face sheets are aimed to examine through experimental testing and finite element simulation in the present work. An improved FGLB is also raised to expose the failure characteristics of graded metamaterial beams. The deformation mode, failure mechanism, and energy absorption of several 3D-printed graded metamaterial beam constructions were carefully explored. The results show that the bending behavior of the novel lattice beam is promoted mainly due to the reinforced structure, especially under mixing reinforcement of FRP and Al face sheets. Additionally, it is discovered that the geometrical parameters and metamaterial core graded direction have a substantial impact on the failure process and energy absorption of FGLB structures. Lastly, multiobjective optimization is used to identify the ideal FGLB design parameters. These accomplishments open the possibility of creating new classes of high-performance metamaterial structures by combining gradient design with additive manufacturing.