I've heard that you shouldn't caulk the outside perimeter of the meter base or an outdoor electrical panel (sealing it to the house siding), because the panel needs to "breath" on the back. I haven't been able to find any specific code reference for this though. Is this code or hearsay?
Do you have siding installed behind the electrical panel? If there is siding behind the panel, then do not caulk it to the siding.
If there is no siding behind the panel, then you can caulk the outside perimeter of the panel. If you have vinyl or steel siding, then you should trim it with J-channel and caulk the J-channel to the electrical panel. If you have any other kind of siding, then you caulk the top and sides but usually not the bottom of the panel to make sure you don't trap any water behind it.
Do not caulk the meter main panel to your siding. I don't know of any code that addresses caulking around it specifically, but this of it like this: If you caulk all around it you've sealed the panel to the siding. The caulking could fail on the top edge. Rain drips down your siding in behind the panel. Where will that rain go? Either into your siding into your wall, or flood into the meter enclosure and short out or damage the meter. The panels keep rain out but are not submersible because there are knockouts and screw holes on the back of it. If you seal all around it, and some caulking fails or water seeps though siding, then you have created a wall of water behind your caulking, the siding, and the enclosure.