@Yashwanth Reddy Yenugu If you are adding external IDP's as Open ID Connect or SAML IDP, you need to use metadata urls.
If the external IDP supports OAuth, you can add it as OAuth IDP in B2C. In that case, you don't need to use any metadata url as you can directly specify endpoints such as Authorization, Token, UserInfo etc.
You can refer to https://learn.microsoft.com/en-us/azure/active-directory-b2c/identity-provider-google-custom?tabs=applications to understand how OAuth IDP can be added to B2C.
-----------------------------------------------------------------------------------------------------------
Please do not forget to "Accept the answer" wherever the information provided helps you. This will help others in the community as well.