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Floating iron (Fe) films are widely found in numerous environments that can form oxic-anoxic boundaries under circumneutral conditions, including wetlands, estuaries, and small lakes. These films play a crucial role in the redox transformations and bioavailability of nutrients, trace metals, and heavy metals. Current studies mainly focus on chemical oxidation during Fe film formation and the characterization of these films. The functional microorganisms and associated microbial processes involved in Fe film formation have yet to be investigated in detail. Here, we investigated the microbial communities and involved microbial processes of floating Fe films in lake wetlands. Ferrihydrite was the dominant Fe(III) phase in films, accompanied by moderate levels of carbon and silicon. The Fe species and microbial analysis indicates that Fe films contain mixed-valent Fe and can form biotically. The analysis of microbial community of these films showed that the dominant genera were Fe-oxidizing and reducing bacteria and methanotrophs, including Leptothrix, Ferriphasclus, Gallionella, Geobacter, and Methylococcales. Leptothrix, Ferriphasclus, and Gallionella, as classical Fe(II)-oxidizing bacteria (FeOB), can oxidize Fe(II) with limited oxygen and form special structures that are closely associated with Fe film formation and are consistent with Fe film morphology. Geobacter can provide a source of Fe(II) for FeOB growth, and Methylococcales can perform methane oxidation to provide energy for Fe cycling. The diversity of floating film community suggest Fe(II) oxidation can trigger carbon fixation, while Fe(III) reduction accelerates Fe and carbon cycling through anaerobic respiration and lithoautotrophic chemosynthesis. These results highlight the contribution of these multiple microbial processes to floating film formation in wetlands. However, further studies are required to fully elucidate the interaction of functional microorganisms involved in floating film formation and their biogeochemical role in wetlands.