Copy metadata to clipboard in the book list only works for one book at a time, the assumption being you will be pasting it into another book.
But you can paste what it copies into something like a text editor, and you'll get something like this
Code:
Title : Quick Start Guide
Title sort : Quick Start Guide
Author(s) : John Schember [Schember, John]
Languages : eng
Timestamp : 2018-12-21T09:05:24+00:00
Published : 0101-01-01T00:00:00+00:00
Comments : calibre Quick Start Guide
Read : Yes
In
Preferences->Shortcuts->Edit metadata you can set keyboard shortcuts for
Copy metadata and
Paste metadata, I have them set to Ctrl+C and Ctrl+V. Or you can select them from the Edit metadata button drop down.
BR