Metal cyanamides/carbodiimides [M_x(NCN)_y], as oxygen/chalcogenide-like compounds, are a new class of inorganic functional materials. The quasi-linear [NCN]^2- anion endows their open and porous crystal structure, unique electronic structure and unique physicochemical properties. They have shown potential applications in many fields including solid-state luminescence, photo/electrocatalysis, and electrochemical energy storage, becoming a research hotspot in recent years. This review outlines the research history of metal cyanamides, introduces the crystal structures and physicochemical properties, summarizes their synthetic methods and strategies, and discusses the applications for electrochemical energy storage, focusing on the electrochemical performance and charge storage mechanism as new-type negative electrode materials for lithium/sodium ion batteries.