For generations, metformin has occupied a privileged place in medicine's imagination — not merely as a glucose-lowering agent, but as a quiet guardian of the heart. The Met-HeFT trial, presented at the 2026 European Society of Cardiology Congress, now asks clinicians to release that assumption. Across 940 patients with heart failure followed for nearly four years, metformin offered no measurable cardiovascular advantage over placebo, suggesting that the drug's long-suspected cardioprotective aura may have been, all along, a reflection of good diabetes management rather than something more.