Background/Objectives: Metformin, a widely used antidiabetic drug, has recently gained attention in dermatology due to its pleiotropic effects. Given the high prevalence, chronicity, and therapeutic challenges of several dermatological conditions, there is growing interest in repurposing metformin as a topical agent with anti-inflammatory, antioxidant, metabolic, and regenerative properties. This narrative review aimed to synthesize and critically analyze the available preclinical and clinical evidence regarding the mechanisms of action, efficacy, safety, and therapeutic potential of topical metformin across different skin disorders. Methods: A literature search was conducted in PubMed and complementary databases for studies published between 2015 and 2025 addressing topical metformin in dermatology, including experimental, observational, interventional, and review articles. Results: The findings indicate that topical metformin has been associated with beneficial biological effects in conditions such as melasma, photoaging, wound healing, psoriasis, acne, skin cancer, and hair disorders, largely through AMPK activation, modulation of inflammation and oxidative stress, inhibition of melanogenesis, enhancement of tissue regeneration, and regulation of immune and metabolic pathways, although evidence remains predominantly preclinical and methodologically heterogeneous. Conclusions: Topical metformin represents a promising investigational multifunctional dermatological agent; however, its clinical translation depends on well-designed randomized controlled trials with standardized formulations, adequate sample sizes, and long-term follow-up to establish its efficacy, safety, and optimal therapeutic protocols.