Abstract: Breast cancer remains one of the most prevalent malignancies among women worldwide, with distant organ metastasis being the leading cause of mortality. The lungs are a common site of metastasis in breast cancer and are associated with significantly poor prognosis. Although notable progress has been made in therapeutic strategies, efficacy remains markedly limited once pulmonary metastasis develops. Therefore, elucidating the molecular mechanisms that drive pulmonary metastasis, characterizing the immune microenvironment, and assessing therapeutic responsiveness are critical. Recent advances in multi-omics approaches-including genomics, transcriptomics, proteomics, metabolomics, and epigenetics-have been widely applied to investigate breast cancer metastasis, offering new insights into the complex molecular networks underlying pulmonary dissemination. This review synthesizes current findings on key genes, proteins, metabolites, and epigenetic regulatory mechanisms involved in the metastatic cascade from a multi-omics perspective.