Global infrastructure development demands sustainable, cost-effective construction solutions with high strength-to-weight ratios. Recent studies show that composite systems using lightweight aluminum and light gauge (LG) steel tubes filled with high-density polyurethane (PU) foam significantly improve compressive and flexural strength due to their composite action and bonding effects. This study investigates the bond characteristics of high-density PU foam-filled aluminum and LG steel tubes, utilizing experimental and numerical evaluations. The findings reveal that confined PU foam exhibits significantly enhanced strength compared to unconfined PU foam, due to triaxial confinement and cell structure rearrangement. The bond between aluminum and high-density PU foam demonstrates reasonable accuracy compared to the steel–concrete bond. Although high-density PU foam-filled steel square tubes show slightly lower compatibility than aluminum circular tubes, both configurations offer substantial improvements in bond performance, validating their flexural and compressive strength enhancements. Further research on LG steel square tubes should be carried out by introducing ribs for improving bond behavior. These composite systems are suitable for applications in structural components, including bracings, solar panel supports, and lightweight shelters. However, the study highlights the potential of using high-density PU foam as an effective infill material in lightweight structural applications, contributing to the advancement of sustainable construction practices.