DNA methylation, a highly conserved epigenetic modification, plays an essential role in regulating gene expression and maintaining genome stability. Aberrations in DNA methylation patterns can significantly disrupt plant developmental processes, often leading to abnormal phenotypes. These methylation states are governed by a dynamic interplay of de novo methylation, maintenance methylation, and active demethylation, mediated by a suite of specialized enzymes operating under distinct regulatory pathways. This review explores the multifaceted roles of DNA methylation in plants. We provide a comprehensive overview of methylases, demethylases, and regulatory factors, elucidating how these components interact within the broader methylation machinery. Key functions of DNA methylation, including its roles in transposon silencing, gene expression regulation, and chromatin interactions, are systematically examined. Additionally, the impact of DNA methylation on plant development is analyzed, with a focus on its involvement in responses to biotic and abiotic stressors. Finally, we discuss the potential applications of DNA methylation in crop improvement, highlighting its promise for advancing modern agricultural practices.