The METS-IR metabolic index demonstrates strong predictive power for cardiac arrhythmias in a comprehensive 22-year analysis of 15,792 middle-aged adults. Each interquartile increase in METS-IR correlated with 49% higher atrial fibrillation risk, 42% higher ventricular arrhythmia risk, and 29% higher bradyarrhythmia risk across 4,496 total cases. This metabolic scoring system, which combines fasting glucose, triglycerides, HDL cholesterol, and BMI, appears to capture cardiovascular risk beyond traditional markers. The finding bridges metabolic dysfunction with electrical heart disease, suggesting insulin resistance pathways may directly influence cardiac conduction systems. For clinical practice, METS-IR could serve as an accessible screening tool since it requires only routine lab values and basic measurements. However, this observational study cannot establish causation, and the population was predominantly older adults from a specific geographic region. As a preprint awaiting peer review, these results require validation before clinical implementation. The research represents incremental but meaningful progress in cardiovascular risk stratification, potentially identifying at-risk individuals before arrhythmias develop.