Current "metacity" packages have the compositor functionality disabled. Right now, you cannot enable compositor features in "metacity" without rebuilding it.
Can't you enable the compositing features in metacity in CLI with
gconftool-2 -s '/apps/metacity/general/compositing_manager' --type bool true
and
Section "Extensions" Option "Composite" EndSection
in the /etc/X11/xorg.conf file as documented on the AiglxOnFedora Wiki page?
When you select "desktop effects", "metacity" gets replaced by "compiz" and vice versa.
What are the plans for the future: enable the compositing features of metacity or replace metacity with compiz? BTW, what will happen when both compiz and metacity with composite features enabled are installed on a system?
Cheers,
Émeric