The atomic dispersing of metal atoms supported on an optimal substrate exhibits an ideal strategy for maximizing metal utilization for catalysis, which is particularly significant for exploiting new catalysts with low cost and high catalytic efficiency. The dramatic development of atomic metal catalysts, including single atom catalysts (SACs), double atoms catalysts (DACs), and triple atoms catalysts (TACs), has spawned two remarkable platforms: (1) bridging homogeneous catalysts and heterogeneous catalysts; (2) linking theoretical calculations and experimental results. In this review, recent syntheses, characterizations, and applications of SACs, DACs, and TACs are highlighted through a focus on various applied substrates. We extensively discuss the synthetic strategies of successfully achieving SACs, DACs, and TACs. Moreover, the opportunities and challenges in developing SACs, DACs, and TACs are pointed out, together with the prospects for the development of atomic catalysis. SACs, DACs, and TACs, heterogeneous catalysts with the advantages of homogeneous catalysts, are ideal models for exploring catalytic mechanisms and further designing catalysts.