Abstract: To address the common challenge that traditional wave-absorbing materials struggle to simultaneously achieve high mechanical load-bearing and efficient electromagnetic stealth, this paper designs and fabricates a metal-fiber composite metamaterial absorber to advance structural-functional integration. Guided by an electromagnetic-mechanical co-design approach, the neutral layer position of the composite cross-section is actively adjusted using the equivalent cross-section method to optimize load transfer. Electromagnetically, the absorption bandwidth is broadened by optimizing a multi-scale concentric-ring frequency-selective surface to excite multiple adjacent resonances. The results show that the fabricated absorber achieves an effective −10 dB bandwidth of 0.47 GHz in the 4–8 GHz range, with an absorption rate exceeding 70% between 4.17 and 6.35 GHz. Mechanically, it exhibits excellent performance: the ultimate flexural strength is 892 MPa, the flexural modulus reaches 1067 MPa, and the compressive strength (705 MPa) is significantly higher than the tensile strength (512 MPa), reflecting an interface-dominated failure mechanism. Compared with fiber-metal laminates without a frequency-selective surface, the proposed structure retains over 89% of its flexural strength and stiffness, successfully realizing effective synergy between microwave absorption and mechanical strength. This study verifies the feasibility of the electromechanical co-design strategy and provides a reliable fabrication route along with experimental support for developing high-performance stealth-capable load-bearing structures.