$ sudo apt-get remove metacity 

Uninstall metacity including dependent package

If you would like to remove metacity and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove metacity 

Use Purging metacity

If you use with purge options to metacity package all the configuration and dependent packages will be removed.

$ sudo apt-get purge metacity 

If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.

$ sudo apt-get purge --auto-remove metacity 

See Also,