<p>Magnetic interactions between iron–sulfur (Fe/S) clusters and transition metal centers such as nickel, molybdenum, and copper play a central role in the function of key metalloenzymes. These interactions, which arise from electronic coupling, spin exchange, and spatial arrangement, directly influence redox behavior and catalytic efficiency. This review highlights three distinct complex enzymes—[NiFe] hydrogenases, mononuclear molybdenum-containing xanthine oxidase (XO) family, and [NiFe] and [MoCu] carbon monoxide dehydrogenases (CODHs)—as paradigms for understanding (Fe/S)-metal center interactions. In [NiFe] hydrogenases, (Fe/S) clusters serve as electron relays that magnetically interact with the catalytic [NiFe] active site. In XO-type enzymes, a mononuclear Mo center is functionally and magnetically coupled to nearby Fe/S clusters, modulating substrate reduction and electron transfer. Similarly, in CODHs, both [NiFe]—and [MoCu]-dependent variants exhibit strong magnetic communication between metal active sites and surrounding Fe/S clusters, crucial for CO₂/CO interconversion. Advanced spectroscopic approaches, particularly electron paramagnetic resonance (EPR) and related techniques, combined with theoretical modelling, have provided deep insights into the electronic structures and dynamic interactions within these metalloenzymes. Understanding these magnetic interactions not only sheds light on fundamental electron-transfer and enzymatic mechanisms but also guides the design of bioinspired catalysts and energy-conversion technologies. </p> Graphical abstract <p></p>