Uncontrolled growth of lithium dendrites and huge volume change during the lithium plating/stripping process as well as poor mechanical properties of the solid electrolyte interphase (SEI) are key obstacles to the development of a stable Li metal anode. Here, an ultralight Mg3N2-modified carbon foam (CF-Mg3N2) was fabricated as a collector to address these issues. The calculated results show that the CF-Mg3N2 composite is relatively stable in terms of energy. Based on the synergistic effect of the three-dimensional skeleton and the lithiophilic nature of Mg3N2, homogeneous lithium deposition/stripping was realized around the foam carbon skeleton with an extremely low nucleation overpotential (∼9.3 mV) and high retention of Coulombic efficiency (99.3%) as well as long cyclability (700 cycles and 3000 h in half and symmetrical cells, respectively). Meanwhile, Mg3N2-CF@Li//LiFePO4 full cells also showed better rate capability and more stable cycling capability than CF@Li//LiFePO4 and Li//LiFePO4 cells, exhibiting extreme practicality. Accordingly, the design concept mentioned in this work provides a far-reaching influence on the development of a stable Li metal anode.