Metformin, a widely used first-line treatment for type 2 diabetes mellitus (T2DM), is known for its efficacy and safety profile. While gastrointestinal disturbances are the most commonly reported with metformin use, dermatologic reactions, particularly severe ones, are rare and underrecognized. We present a case of a 45-year-old male with a history of atrial fibrillation who developed acute generalized exanthematous pustulosis (AGEP) after initiating metformin for prediabetes.