Redox-active metabolites (RAMs) including phenazines, flavins, quinones, and emerging peptide-derived cofactors, have long been viewed through the narrow lens of toxicity or antimicrobial activity. However, recent studies have reframed these small molecules as integral agents of microbial communication. By undergoing reversible oxidation?reduction reactions, RAMs reshape environmental redox potentials and, in turn, modulate gene expression, biofilm development, nutrient acquisition, and interspecies interactions. This article highlights the evolving understanding of RAMs as signalling mediators, summarizes new discoveries from 2023?2025, and discusses future challenges in decoding their ecological and biomedical significance.