To uninstall metacity-themes just follow these instructions.
sudo apt-get remove metacity-themes
This will remove just the metacity-themes package itself.
sudo apt-get remove --auto-remove metacity-themes
This will remove the metacity-themes package and any other dependant packages which are no longer needed.
If you also want to delete your local/config files for metacity-themes then this will work.
sudo apt-get purge metacity-themes
Or similarly, like this metacity-themes
sudo apt-get purge --auto-remove metacity-themes
|Maintainer||Mauro Lizaur <email@example.com>|
|Description||Themes for the Gtk2 metacity window manager|