Metal?air and metal?sulfur batteries (MABs/MSBs) represent one of the most efficient-energy storage technologies, with high round trip efficiency, a long life cycle, fast response at peak demand/supply of electricity, and decreased weight due to the use of atmospheric oxygen as one of the main reactants. This book presents an overview of the main MABs/MSBs from fundamentals to applications. Recent technological trends in their development are reviewed. It also offers a detailed analysis of these batteries at the material, component, and system levels, allowing the reader to evaluate the different approaches of their integration. The book provides a systematic overview of the components, design, and integration, and discusses current technologies, achievements, and challenges, as well as future directions. Each chapter focuses on a particular battery type including zinc?air batteries, lithium?air batteries, aluminum?air batteries, magnesium?air batteries, lithium?sulfur batteries, and vanadium?air redox flow batteries, and metal?sulfur batteries.