One way to find meta packages is to use "apt-cache search".
Here is an example of a search for meta packages having to do with Xfce4;
root@debian:/home/tom# apt-cache search "meta" "xfce4"
shiki-colors-xfwm-theme - Xfwm/Xfce4 theme based on the Shiki-Colors Metacity theme
xfce4 - Meta-package for the Xfce Lightweight Desktop Environment
xfce4-goodies - enhancements for the Xfce4 Desktop Environment
The search patterns must be within quotations marks.
See "man apt-cache" for more info.
Also "info apt-cache".