<p>Metal-iodine batteries have attracted widespread attention due to their long cycle life, high energy density, remarkable charging capability and low self-discharge rate. Nevertheless, this development is hampered by the challenges of the iodine cathode and metal anode, including the hydrogen evolution reaction (HER), sluggish kinetics, shuttle effect of polyiodine ion at the cathode and dendrite formation, corrosion and passivation at the anode. This review summarizes recent developments in metal-iodine batteries, including zinc-iodine batteries, lithium-iodine batteries, sodium-iodine batteries, etc. The challenges in the cathode, anode, electrolyte and separator of metal-iodine batteries are discussed, along with the corresponding design and synthesis strategies and specific methods to improve the electrochemical performance. Selecting appropriate cathode hosts, constructing surface protective layers, adding anode additives, making three-dimensional anode designs and employing better electrolytes and functional separators to obstruct the production and shuttling of polyiodine ions are highlighted. Finally, future guidelines and directions for the development of metal-iodine batteries are proposed.</p> Graphical abstract <p></p>