Optional subjects in the UPSC Civil Services Exam play a crucial role in determining overall scores, potentially influencing the final ranking. Candidates need to choose optional subjects wisely, matching their interests and strengths. A comprehensive understanding of the subject matter enhances performance in both the Mains and interview. The syllabus of optional subjects often requires in-depth study and specialization, allowing candidates to showcase expertise. Additionally, good performance in optional papers can significantly bolster overall merit during the selection process.