Microbial communities exhibit high taxonomic diversity, raising questions about species coexistence and community function. Functional redundancy, where multiple taxa perform the same metabolic function, contrasts with the expectation of distinct metabolic niches. Taxonomic variability in function across environments is often attributed to ecological drift, but the authors argue that both patterns are emergent properties of open microbial systems, driven by biotic interactions and environmental processes. Microorganisms are highly diverse and metabolically versatile, driving Earth's biogeochemical cycles. However, our understanding of microbial systems remains limited. Functional community profiling simplifies microbial systems for modeling and reveals community structuring across environmental gradients. Recent studies show that certain metabolic functions are strongly coupled to environmental factors and may decouple from species assemblages. Functional redundancy is widespread, with multiple taxa performing similar functions. Taxonomic and functional compositions are often decoupled, with taxonomic variation not necessarily reflecting functional variation. This decoupling is due to factors beyond taxonomy, such as environmental conditions and metabolic pathways. Functional redundancy is a common feature of microbial systems, with functions often performed by multiple taxa. Functional redundancy is not a sign of neutrality but reflects ecological diversity. Mechanisms promoting functional redundancy include niche differentiation, trade-offs between traits, and interactions like phage predation. Functional redundancy is not explained by ecological drift but by ecological differences and dispersal. The study highlights the importance of functional redundancy in microbial systems, emphasizing the need to consider metabolic functions rather than just taxonomy in microbial ecology. The findings suggest that functional redundancy is a key aspect of microbial systems, with implications for understanding community assembly and biogeochemical processes.Microbial communities exhibit high taxonomic diversity, raising questions about species coexistence and community function. Functional redundancy, where multiple taxa perform the same metabolic function, contrasts with the expectation of distinct metabolic niches. Taxonomic variability in function across environments is often attributed to ecological drift, but the authors argue that both patterns are emergent properties of open microbial systems, driven by biotic interactions and environmental processes. Microorganisms are highly diverse and metabolically versatile, driving Earth's biogeochemical cycles. However, our understanding of microbial systems remains limited. Functional community profiling simplifies microbial systems for modeling and reveals community structuring across environmental gradients. Recent studies show that certain metabolic functions are strongly coupled to environmental factors and may decouple from species assemblages. Functional redundancy is widespread, with multiple taxa performing similar functions. Taxonomic and functional compositions are often decoupled, with taxonomic variation not necessarily reflecting functional variation. This decoupling is due to factors beyond taxonomy, such as environmental conditions and metabolic pathways. Functional redundancy is a common feature of microbial systems, with functions often performed by multiple taxa. Functional redundancy is not a sign of neutrality but reflects ecological diversity. Mechanisms promoting functional redundancy include niche differentiation, trade-offs between traits, and interactions like phage predation. Functional redundancy is not explained by ecological drift but by ecological differences and dispersal. The study highlights the importance of functional redundancy in microbial systems, emphasizing the need to consider metabolic functions rather than just taxonomy in microbial ecology. The findings suggest that functional redundancy is a key aspect of microbial systems, with implications for understanding community assembly and biogeochemical processes.