With the ever-growing demand for high energy density and high safety of energy storage technologies, all-solid-state lithium metal batteries (ASSLMBs) including all-solid-state lithium ion batteries (ASSLIBs) and all-solid-state lithium–sulfur batteries (ASSLSBs) have received considerable attention in recent years. To realize ASSLMBs, various solid-state electrolytes have been rapidly developed. Among them, sulfide electrolytes (SEs) demonstrate the highest ionic conductivity (>10 mS·cm–1) and the most favorable mechanical properties. However, the commercialization of SE-based ASSLMBs has been stymied by sluggish interfacial ion and electron transport kinetics, which arises from the detrimental interfacial reactions, poor interfacial solid–solid contact, and lithium dendrite growth. To overcome the interfacial challenges, an insightful understanding of the complex interfacial ion and electron transport processes in SE-based ASSLMBs is of the foremost importance. Although most of the previous review papers underscored the interfacial challenges and summarized the corresponding strategies, a fundamental understanding of the interfacial ions and electron-transport kinetics in SE-based ASSLMBs has not yet been presented. This Account therefore primarily summarizes our recent understanding of SE-based ASSLMBs from the perspectives of interfacial ion and electron transport, aiming to provide an insightful understanding of interfacial kinetics.