Abstract: Amidst the rapid development of renewable energy, the intermittency and instability of energy supply pose severe challenges and impose higher requirements on energy storage systems. Among the various energy storage technologies, the coupled approach of power-to-hydrogen (H2) and underground H2 storage (UHS) offers advantages such as extended storage duration and large-scale capacity, making it highly promising for future development. However, during UHS, particularly in porous media, microbial metabolic processes such as methanogenesis, acetogenesis, and sulfate reduction may lead to H2 consumption and the production of byproducts. These microbial activities can impact the efficiency and safety of UHS both positively and negatively. Therefore, this paper provides a comprehensive review of experimental, numerical, and field studies on microbial interactions in UHS within porous media, aiming to capture research progress and elucidate microbial effects. It begins by outlining the primary types of UHS and the key microbial metabolic processes involved. Subsequently, the paper introduces the experimental approaches for investigating gas–water–rock–microbe interactions and interfacial properties, the models and simulators used in numerical studies, and the procedures implemented in field trials. Furthermore, it analyzes and discusses microbial interactions and their positive and negative impacts on UHS in porous media, focusing on aspects such as H2 consumption, H2 flow, and storage safety. Based on these insights, recommendations for site selection, engineering operations, and on-site monitoring of UHS, as well as potential future research directions, are provided.