AbstractMetallic phase 2D molybdenum disulfide (MoS2) is an emerging class of materials with remarkably higher electrical conductivity and catalytic activities. The goal of this study is to review the atomic structures and electrochemistry of metallic MoS2, which is essential for a wide range of existing and new enabling technologies. The scope of this paper ranges from the atomic structure, band structure, electrical and optical properties to fabrication methods, and major emerging applications in electrochemical energy storage and energy conversion. This paper also thoroughly covers the atomic structure–properties–application relationships of metallic MoS2. Understanding the fundamental properties of these structures is crucial for designing and manufacturing products for emerging applications. Today, a more holistic understanding of the interplay between the structure, chemistry, and performance of metallic MoS2 is advancing actual applications of this material. This new level of understanding also enables a myriad of new and exciting applications, which motivated this review. There are excellent reviews already on the traditional semiconducting MoS2, and this review, for the first time, focuses on the uniqueness of conducting metallic MoS2 for energy applications and offers brand new materials for clean energy application.