You may already know how to do this but a lot of folks are unaware the the metronome is just another stereo buss that you can create from scratch.
If your metronome is missing from the buss pane just insert a new stereo buss.
Name it metronome.
Assign the output to master or better yet directly to "audio interface output 1/2."
Open the metronome dialog and choose "audio" and then assign the output to the new metronome bus. Done.
If you would like to use it in a live set up and you have a multi output audio interface you can assign the metronome output to an unused port like 3/4 and send that to your in ear monitor mix. You might want to change the sound to something a little less obnoxious than the default clip clop.