This study is a randomized, controlled, open-label, multicenter, phase II superiority clinical trial. The planned study population consists of participants with HER2-positive recurrent or metastatic breast cancer who have not previously received systemic therapy for advanced disease (participants who have undergone one prior endocrine treatment regimen are eligible for enrollment). The study aims to compare the efficacy and safety of JSKN003 versus trastuzumab combined with pertuzumab and docetaxel as first-line treatment for participants with HER2-positive recurrent or metastatic breast cancer.