This study comprehensively investigates the performance of an innovative metallic sandwich structure featuring a square metallic lattice core alternately filled with lightweight concrete under blast loading conditions. Unlike previous research primarily focused on fully metallic hollow frameworks, this work integrates lightweight concrete and steel in the core to enhance energy absorption and reduce deformation caused by blast waves. Detailed numerical simulations were conducted using ABAQUS/Explicit 2024, evaluating the structural response to TNT explosive charges of 1, 2, and 3 kg. Critical parameters including upper and lower face plate displacements, equivalent plastic strain (PEEQ), and absorbed energies such as viscous, plastic, artificial, and total were systematically measured and compared with the reference results reported by Derseh et al. (2023). The results indicate that incorporating lightweight concrete in an alternating configuration significantly reduces plate displacements, lowers equivalent plastic strain, and achieves a more uniform energy distribution across the structure. Time-history displacement analysis demonstrates that the proposed hybrid model stabilizes faster after the blast and exhibits reduced oscillation amplitude, reflecting enhanced dynamic performance and higher damping capacity. Furthermore, the total dissipated energy in the hybrid configuration is lower than that of the fully metallic reference model, while the energy distribution is more effective throughout the structure. These findings demonstrate that an alternating lightweight concrete-metal core represents an effective and innovative approach to improving blast resistance in sandwich structures under extreme dynamic loading. In addition to enhancing safety, this design reduces structural weight, lowers construction costs, and facilitates implementation. Therefore, the proposed system serves as a lightweight, strong, efficient, and economical solution for blast-resistant structures, particularly in military, industrial, and sensitive urban applications. Its practical adaptability, optimized energy absorption, and improved structural resilience make it a highly suitable option for modern engineering designs requiring high performance under severe loading conditions.