Recent experiments reported the evidence of robust zero mode trapped by different defects such as vortex, crystalline domain wall and magnetic impurity in some iron-based superconductors. Here, We present a unified physical picture for understanding the above phenomena. In particular, we elaborate on the theory of magnetic impurity-bound robust zero-energy states, use it to interpret the experimental controversies in Fe(Te, Se), and extend it to understand the robust zero modes induced by V vacancies in the kagome superconductor CsV3Sb5. Finally, we discuss the symmetry-breaking Kondo resonance states induced by Cr impurities in CsV3Sb5, which are likely associated with loop current order.

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