Good advice from Sirtel and Bookcat to a good question.
I have never considered to insert my metadata in the front of the book.
When the metadata is as you want it then you should use the Calibre's
Polish feature.
One of the options in
Polish is to insert a Metadata jacket in the start of the book.
Polishing will/can also update the cover picture. You don't have to convert the books in order to insert a metadata jacket.