Mobile genetic elements (MGEs) play a crucial role in horizontal gene transfer (HGT) in bacteria, facilitating rapid evolution and adaptation. MGEs include plasmids, integrative and conjugative elements (ICEs), transposons, insertion sequences, and bacteriophages. The spread of antimicrobial resistance genes (ARGs) is primarily attributed to HGT through MGEs, posing a significant threat to public health. This mini-review provides an overview of the mechanisms by which MGEs mediate HGT, focusing on the behavior of conjugative plasmids and recent methodologies for tracing MGE dynamics. Understanding the mechanisms underlying HGT and the role of MGEs in bacterial evolution is essential for developing strategies to combat the spread of ARGs. The review covers the general features of representative MGEs, including bacteriophages, plasmids, chromosomally integrated MGEs (ciMGEs), transposons, and integrons. It discusses the host range of MGEs and their behaviors in natural environments, highlighting the importance of new-generation sequencing technologies and culture-independent methods for studying MGEs. The co-evolution of plasmids and their hosts is also explored, including compensatory mutations that resolve the 'plasmid paradox' and the fitness costs of plasmids and ARGs. Finally, the authors discuss future challenges and perspectives, emphasizing the need for standardized annotation and classification of MGEs and the potential of single-cell genomics in environmental studies.Mobile genetic elements (MGEs) play a crucial role in horizontal gene transfer (HGT) in bacteria, facilitating rapid evolution and adaptation. MGEs include plasmids, integrative and conjugative elements (ICEs), transposons, insertion sequences, and bacteriophages. The spread of antimicrobial resistance genes (ARGs) is primarily attributed to HGT through MGEs, posing a significant threat to public health. This mini-review provides an overview of the mechanisms by which MGEs mediate HGT, focusing on the behavior of conjugative plasmids and recent methodologies for tracing MGE dynamics. Understanding the mechanisms underlying HGT and the role of MGEs in bacterial evolution is essential for developing strategies to combat the spread of ARGs. The review covers the general features of representative MGEs, including bacteriophages, plasmids, chromosomally integrated MGEs (ciMGEs), transposons, and integrons. It discusses the host range of MGEs and their behaviors in natural environments, highlighting the importance of new-generation sequencing technologies and culture-independent methods for studying MGEs. The co-evolution of plasmids and their hosts is also explored, including compensatory mutations that resolve the 'plasmid paradox' and the fitness costs of plasmids and ARGs. Finally, the authors discuss future challenges and perspectives, emphasizing the need for standardized annotation and classification of MGEs and the potential of single-cell genomics in environmental studies.