Finding journals discussing metaphysics for UPSC Philosophy Optional can be a challenging task, but with the right approach, you can discover valuable resources. Here are some steps to help you in your search:

1. Online Databases:
- JSTOR: JSTOR is a widely recognized online library that provides access to numerous academic journals. It covers various disciplines, including philosophy. To access JSTOR, you can visit their official website and create an account. Once logged in, you can search for specific keywords related to metaphysics.
- PhilPapers: PhilPapers is an extensive online research hub for philosophy. It contains a vast collection of papers, articles, and journals. You can utilize its search feature to find relevant metaphysics journals. Additionally, PhilPapers allows you to filter results based on specific categories, such as metaphysics, ontology, and epistemology.

2. University Libraries:
- University libraries often have access to several academic databases and resources. If you have access to a university library, you can search their online catalog or speak to a librarian for assistance. They can guide you in locating relevant metaphysics journals or provide access to online databases specifically designed for academic research.

3. Academic Institutions:
- Check the websites of renowned academic institutions offering philosophy programs. Many universities have their own publications or journals dedicated to philosophy. These journals often include articles on metaphysics. You can search for these journals on the respective university websites and explore their archives.

4. Philosophy Associations and Societies:
- Philosophy associations and societies publish journals that focus on different branches of philosophy. For metaphysics, you can explore journals published by organizations like the American Philosophical Association (APA), British Society for Metaphysics (BSM), or International Association for Metaphysics (IAM). Visit their websites to find information about their journals and access their publications.

Remember, while conducting your research, it is essential to critically evaluate the information you find. Pay attention to the credibility of the sources, the authors' qualifications, and the relevance of the content to your study. This will help you select the most reliable and suitable journals for your UPSC Philosophy Optional preparation.