Microbial evolution through horizontal gene transfer (HGT) is driven by mobile genetic elements (MGEs), which include plasmids, integrative and conjugative elements (ICEs), transposons, insertion sequences, and bacteriophages. These elements facilitate rapid bacterial evolution and adaptation, particularly in the spread of antimicrobial resistance genes (ARGs), which pose a serious threat to public health. This mini-review summarizes the mechanisms by which MGEs mediate HGT in microbes, focusing on the behavior of conjugative plasmids in different environments and recent methodologies for tracing MGE dynamics. Understanding HGT mechanisms and the role of MGEs in bacterial evolution is crucial for developing strategies to combat ARG spread. MGEs play a key role in bacterial evolution through HGT, with bacteriophages, plasmids, transposons, and integrons being the main types. Bacteriophages can transfer genes through integration and excision, while plasmids are transmitted via conjugation. Transposons move between replicons via transposase activity, and integrons facilitate the spread of ARGs by harboring gene cassettes. The host range of MGEs varies, with some elements having broader ranges than others. Understanding these ranges is essential for elucidating how MGEs spread among bacteria and contribute to evolution. Recent studies have shown that plasmids can be identified and classified using various methods, including replicon typing and MOB/MPF typing. The behavior of plasmids in natural environments is influenced by factors such as replication systems and host compatibility. Plasmids containing transposons and integrons are particularly important in microbial evolution, as they can transfer genes between bacteria. Techniques such as exogenous plasmid capture and fluorescent protein-based methods have been used to identify and track plasmids in environmental samples. The co-evolution of plasmids and their hosts is a complex process, with compensatory mutations playing a key role in resolving the 'plasmid paradox.' These mutations can reduce the fitness cost of plasmid carriage, allowing plasmids to persist in host populations. The spread of ARGs is also influenced by the fitness cost of plasmid carriage, with some plasmids being more advantageous in certain environments. Rearrangements and deletions of plasmid DNA can also affect host fitness and contribute to the adaptation of bacteria. Future research should focus on developing methods to identify MGEs and their hosts from metagenomic data, standardizing MGE annotation and classification, and utilizing single-cell genomics to better understand MGE dynamics. Advances in sequencing technology and analytical methods have enhanced our understanding of MGEs and their role in bacterial evolution and adaptation.Microbial evolution through horizontal gene transfer (HGT) is driven by mobile genetic elements (MGEs), which include plasmids, integrative and conjugative elements (ICEs), transposons, insertion sequences, and bacteriophages. These elements facilitate rapid bacterial evolution and adaptation, particularly in the spread of antimicrobial resistance genes (ARGs), which pose a serious threat to public health. This mini-review summarizes the mechanisms by which MGEs mediate HGT in microbes, focusing on the behavior of conjugative plasmids in different environments and recent methodologies for tracing MGE dynamics. Understanding HGT mechanisms and the role of MGEs in bacterial evolution is crucial for developing strategies to combat ARG spread. MGEs play a key role in bacterial evolution through HGT, with bacteriophages, plasmids, transposons, and integrons being the main types. Bacteriophages can transfer genes through integration and excision, while plasmids are transmitted via conjugation. Transposons move between replicons via transposase activity, and integrons facilitate the spread of ARGs by harboring gene cassettes. The host range of MGEs varies, with some elements having broader ranges than others. Understanding these ranges is essential for elucidating how MGEs spread among bacteria and contribute to evolution. Recent studies have shown that plasmids can be identified and classified using various methods, including replicon typing and MOB/MPF typing. The behavior of plasmids in natural environments is influenced by factors such as replication systems and host compatibility. Plasmids containing transposons and integrons are particularly important in microbial evolution, as they can transfer genes between bacteria. Techniques such as exogenous plasmid capture and fluorescent protein-based methods have been used to identify and track plasmids in environmental samples. The co-evolution of plasmids and their hosts is a complex process, with compensatory mutations playing a key role in resolving the 'plasmid paradox.' These mutations can reduce the fitness cost of plasmid carriage, allowing plasmids to persist in host populations. The spread of ARGs is also influenced by the fitness cost of plasmid carriage, with some plasmids being more advantageous in certain environments. Rearrangements and deletions of plasmid DNA can also affect host fitness and contribute to the adaptation of bacteria. Future research should focus on developing methods to identify MGEs and their hosts from metagenomic data, standardizing MGE annotation and classification, and utilizing single-cell genomics to better understand MGE dynamics. Advances in sequencing technology and analytical methods have enhanced our understanding of MGEs and their role in bacterial evolution and adaptation.