No such thing exists.
Ctrl+3 = Keywords
Ctrl+4 = Metadata
Library Panels can be selected by [Ctrl+Number]
Wonderful!! Thank you so much. This is really a help.
Yes, the shortcuts for Panel selection are somewhat cryptic and hard to find.
Find a PDF of shortcuts here-
My first read of your question I thought you were trying to put keywords INTO metadata with a keyboard shortcut. Generally not possible as in the reply from dj_paige
Except that you can use a numeric keypad (1-9) to easily add keywords (by keyboard) from a Keyword SET-
When you hold down the [ALT] key you will see the grid of the Set show the numbers 1-9, as on the numeric keypad. So eg. [ALT numeric 9] would add the keyword "Reception", [ALT numeric2] would add "Groom".
A useful feature for situations like a wedding job, etc.