The increasing prevalence of antimicrobial resistance (AMR) has intensified the demand for novel therapeutic strategies. Metal complexes have emerged as promising agents due to their unique chemical properties and diverse modes of action. This review presents an in-depth analysis of metal complexes—including those of cobalt(III), copper(II), palladium(II), and silver—as antimicrobial, antiviral, and antiparasitic agents. We highlight their mechanisms of action, structural advantages, and efficacy against pathogens including bacteria, viruses (e.g., herpes simplex), and protozoan parasites (e.g., Trypanosoma cruzi). Emphasis is placed on the structural design, biological interactions, and potential for future therapeutic development. This review also includes a summary of recent findings with supportive tables to provide comparative insights.