As HER2 is currently the only established therapeutic target, this review sought to provide a comprehensive overview of first-line therapy, second-line therapy, and subsequent palliative systemic therapy for metastatic GC in HER2-positive and HER2-negative GC from the pivotal clinical trials reported by January 2023 and present recent evidence for perioperative (neoadjuvant) and adjuvant therapy. Here, ERBB2 is linked to gastric cancer.