The need for energy storage technologies that meet the demands for safety, sustainability, and high energy density has spurred increased interests in rechargeable Mg batteries. However, verification of their potential remains hampered by the absence of practical components. Recently, an unconventional research direction that deviates from the mainstream path has emerged and is redefining the boundaries of what can be accomplished in Mg batteries. Herein, we analyze this direction with a focus on fundamental phenomena with an aim to reveal new opportunities that can overcome long-standing challenges and unveil unaddressed issues. The topics covered encompass: (1) realizing efficient single salt Mg electrolytes that mimic those used in typical Li- and Na-ion batteries, (2) discovery of important concomitant mechanisms and previously unanticipated interfacial phenomena, and (3) identification of often overlooked bottlenecks in Mg cathodes and alternative anodes. In closing, we put forward our proposal for R&D focuses to help realize practical Mg batteries.