Human heart is physiologically and metabolically one of the most active organs. It consumes 5 kg ATP per day, of which fatty acids provides two third and glucose and lactate provide one third. Thus, metabolic substrates and metabolites, by participating in bioenergetic pathways, are considered to play important role in cardiac electrophysiology. In many physiological investigations metabolites are often considered as passive bystanders whose sole purpose is generating ATP. Increasing evidence, however, suggests that alteration of metabolic substrates or accumulation of metabolites in heart, particularly during metabolic disorders such as insulin resistance, obesity and diabetes, could be independent risk factors for electrophysiological conditions such as atrial fibrillation and ventricular tachycardia. This is also supported by recent findings that the mutation in metabolic gene causes Brugada syndrome which was previously thought to be exclusively ion channel related disorder. Thus, studying cardiac electrophysiology in context of metabolic alteration could provide important clues to understanding mechanisms of arrhythmia. Here, by combining single cell physiological studies (patch-clamp and Ca²⁺ imaging) and in vivo and ex vivo monitoring of cardiac rhythm, we provide evidence to suggest that altering metabolic substrates (glucose, lactic acid and pyruvate) could have important physiological consequences, particularly in a system with impaired electrophysiological conditions. Furthermore, some intracellular metabolites such as NAD⁺/NADH, ATP/ADP and lipid intermediates were found to exert unexpected electrophysiological effects in heart. Finally, our experimental evidence derived from multidisciplinary approaches of gene expression, metabolomic and lipidomic in parallel with electrophysiological studies show that genetic ablation of transcriptional regulator of metabolic gene causes cardiac arrhythmia. Our studies provide new insights into the mechanism of cardiac arrhythmia that could explain increase cardiac mortality in metabolic diseases such as diabetes, insulin resistance and obesity.