Metal–polymer adhesion technologies are crucial across various industries for achieving lightweight design while maintaining high functionality. Hot-melt adhesives are widely preferred due to their rapid bonding and solvent-free processing; however, surface energy mismatch makes single-adhesive design for dissimilar interfaces challenging. Conventional solutions often suffer from poor recyclability or require complex synthesis routes. Here, we propose an upcycled, cost-effective polyethylene (PE)–based hot-melt adhesive derived from commodity polymers. The adhesive is simply modified without additional synthesis by controlled PE oxidation to introduce hydroxyl groups, followed by boric acid incorporation to form dynamic boronic ester bonds. The resulting covalent adaptable network interacts with both metal oxide layers and hydroxyl-functionalized polymer substrates, enabling strong interfacial adhesion while maintaining sufficient cohesive strength within the adhesive.