Background: The dissemination of pathogens carrying genetic elements such as antimicrobial resistance genes (ARGs), mobile-genetic elements (MGEs), virulome and methylome have a negative impact on food and environment safety, water quality and animal and human health. The applications of metagenomics to monitor and identify the prevalence/endemicity and emergence of these pathogenic agents from different sources were examined. Methods: Articles published in English language up to October 2020 were searched for on PubMed. Qualitative and quantitative data extracted from the included articles were translated into charts and maps. GraphPad Prism 9.0.2 was used to undertake statistical analysis using descriptive and column statistics, Chi-square, ANOVA, Wilcoxons signed-rank, and one-sample t-test. Results: In all, 143 articles from 39 countries from Europe, America, Asia, and Africa were quantitatively analysed. Metagenomes from sewage/wastewater, surface water samples (ocean, sea, river lake, stream and tap water), WWTP, effluents and sludge samples contained pathogenic bacteria (Aeromonas, Acinetobacter, Pseudomonas, Streptococcus, Bacteroides, Escherichia coli, Salmonella enterica, Klebsiella pneumoniae and Acinetobacter baumannii), viruses (Adenovirus, Enterovirus, Hepatovirus, Mamastrovirus and Rotavirus) and parasites (Acanthamoeba, Giardia, Entamoeba, Blastocystis and Naegleria). Integrons, plasmids, transposons, insertion sequences, prophages and integrative and conjugative elements were identified. ARGs mediating resistance to important antibiotics, including β-lactams, aminoglycosides, fluoroquinolones, and tetracycline, and virulence factors such as secretion system, adherence, antiphagocytosis, capsule, invasion, iron uptake, hemolysin, and flagella. Conclusion: Clinically important pathogens, ARGs, and MGEs were identified in diverse clinical, environmental, and animal sources through metagenomics, which can be used to determine the prevalence and emergence of known and unknown pathogens and ARGs.