In the search for carbon-free renewable and sustainable fuels, an underexplored option is the use of metals as recyclable energy carriers. Metals can be produced via electrolytic processes at efficiencies comparable to hydrogen- or carbon-based carriers; metals are energy-dense and stable solids that are easy to transport and store. The key limitation to the use of metals as recyclable fuels is the lack of any mature technology for power generation using metal fuels. This chapter will review the overall concept of metals as recyclable fuels, discuss the possible options for metal-fueled power-generation systems, and identify the remaining science and technology gaps.