Problem:
How do I use Plex URL commands to show all movie metadata in xml format?
Solution:
Quite simply paste the following into the browser on your Plex server (changing the token and key):
http://127.0.0.1:32400/library/sections/<your movie key number here>/all?X-Plex-Token=<your token here>
You can now right click on the page and save as .xml