It depends on which half of MetCom you want to monitor. The G4/G5 are extraordinary in being able to receive weaker sites so I believe you should be able to receive at least one of the more ideal sites before needing to resort to programming some of the other sites which may not have some talkgroups.
For MetCom and South Metro Fire Rescue, I would suggest the following sites from more preferable to less preferable and are what I use for my South Metro specific system.
I do not have experience with this site and I am not completely sure if the East MetCom operations talkgroups will be consistently found on this site since it is more rural there are less radios that might routinely affiliate to those talkgroups.
Same as Byers, except this is pretty much at the edges of where East MetCom dispatches for and most likely carries less traffic than Byers.
As for looking up a map, I would suggest looking at the site map built into the trunked radio system database for an idea of where the sites are located with the most ideal sites being as close to the center of the area you would like to monitor. You can find a link to these maps listed immediately below the System Frequencies heading and before where any of the site information is listed.