[OS X Emacs] Using Mac's Command key as Ctrl key

[Gaston Fiore]

Hello,

I was wondering whether there's a way to customize Aquamacs so that
Mac's Command key becomes a Ctrl key. For example, to open a file, I'd
use Command-X Command-F, instead of the standard Ctrl-X Ctrl-F.

Thanks a lot for your help,

-Gaston