A lean electrolyte design is one of the central aims of current research on lithium metal batteries (LMBs) based on liquid electrolytes because of its high impact on augmenting a gravimetric energy density. However, the lean electrolyte condition exacerbates the capacity fade caused by the degradation of the electrolyte and lithium metal electrode, presenting formidable challenges. In this review, we describe the challenges of lean electrolyte LMBs based on previous understanding of Li metal electrodes and recently found features of lean electrolyte LMBs. We summarize the recent progress in lean electrolyte LMBs explaining the physicochemical concepts of these approaches. Insights and possible research directions are presented to inspire innovation.