Ketone bodies are one of the main molecules of physiological homeostasis. They are auxiliary metabolic fuel that replaces glucose in most extrahepatic tissues in situations of limited carbohydrate availability, or inability to utilize them. These molecules are produced by ketogenesis in the liver, while the metabolic process of ketolysis exploits ketone bodies in extrahepatic tissues for energy purposes. In addition, ketone bodies are also intermediates on multiple metabolic pathways and signaling molecules that, through surface receptors, epigenetic regulation of gene transcription, and yet unknown mechanisms, influence many cellular functions. These noncanonical actions of ketone bodies give an image of powerful molecules that offer therapeutic applications in a variety of health conditions through modulation of inflammation oxidative damage, histone acetylation, alteration of cellular redox status, and other mechanisms. This also extends the understanding of physiological role of ketone bodies beyond that of maintaining energy homeostasis and points to their pleiotropic potential, which is why ketone bodies are today assigned the role of mediators of metabolic health. Therefore, the purpose of this thesis is to describe the metabolism and pleiotropic roles of ketone bodies from a traditional and modern point of view and to highlight the physiological and therapeutic potential of these molecules.