Abstract: Ammonia, with its high hydrogen content, ease of liquefaction, and potential for carbon-free utilization, is regarded as an important carrier linking renewable hydrogen production, hydrogen storage and transportation, and ammonia-based energy utilization. Ammonia decomposition can be employed not only for on-site hydrogen release but also as a pre-cracking process prior to combustion to regulate the composition of NH?/H?/N? fuel mixtures. However, this reaction is strongly endothermic and kinetically limited at low temperatures, making it difficult to simultaneously achieve high conversion and high hydrogen production rates under relatively mild conditions. In addition, catalysts are susceptible to hydrogen/nitrogen poisoning, metal sintering, and reconstruction of active structures, which makes it challenging to reconcile low-temperature activity with long-term stability. To address these issues, this review systematically summarizes recent progress in Ru-, Fe-, Co-, and Ni-based metal catalysts from four aspects: intrinsic activity, number of active sites, chemical stability, and thermal stability. The mechanisms underlying representative structural optimization strategies are also analyzed. Finally, in view of the remaining challenges, future research directions are discussed, including the dynamic evolution of active sites, multi-objective rational catalyst screening, and stability evaluation under realistic operating conditions. This review aims to provide useful guidance for the structural design and stability enhancement of metal catalysts for ammonia decomposition.