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Designing novel single‐atom catalysts (SACs) supports to modulate the electronic structure is crucial to optimize the catalytic activity, but rather challenging. Herein, a general strategy is proposed to utilize the metalloid properties of supports to trap and stabilize single‐atoms with low‐valence states. A series of single‐atoms supported on the surface of tungsten carbide (M‐WCx, M=Ru, Ir, Pd) are rationally developed through a facile pyrolysis method. Benefiting from the metalloid properties of WCx, the single‐atoms exhibit weak coordination with surface W and C atoms, resulting in the formation of low‐valence active centers similar to metals. The unique metal‐metal interaction effectively stabilizes the low‐valence single atoms on the WCx surface and improves the electronic orbital energy level distribution of the active sites. As expected, the representative Ru‐WCx exhibits superior mass activities of 7.84 and 62.52 A mgRu−1 for the hydrogen oxidation and evolution reactions (HOR/HER), respectively. In‐depth mechanistic analysis demonstrates that an ideal dual‐sites cooperative mechanism achieves a suitable adsorption balance of Had and OHad, resulting in an energetically favorable Volmer step. This work offers new guidance for the precise construction of highly active SACs. [ABSTRACT FROM AUTHOR]