<p>Metagenomics has significantly advanced our understanding of microbial life by enabling the direct analysis of environmental DNA, thereby deciphering the vast microbial dark matter comprising unknown and uncultivable microbial diversity that remains inaccessible through conventional culture-dependent methods. The culture-independent approach provides a comprehensive view of microbial composition, function, and evolution, facilitating discoveries across environmental and clinical domains. Recent developments in high-throughput sequencing, hybrid long-read assemblies, and AI/ML-based genome binning have enhanced our understanding to reconstruct complete genomes, predict metabolic pathways, and engineer microbial consortia. This review summarizes the impact of metagenomics on environmental and therapeutic microbiology, emphasizing its contributions in the field of bioremediation, greenhouse gas mitigation, sustainable agriculture, industrial enzyme discovery, and novel drug development. It further explores metagenomics-driven innovations in pathogen detection, antimicrobial resistance surveillance, and multi-omics integration. Furthermore, it discusses methodological developments, computational challenges, and translational limitations, offering future perspectives for harnessing metagenomic insights in sustainable biotechnology and precision medicine.</p> Graphical abstract <p></p>