From the producer:
Upgrade your Metroguide to a "Gold" product with MetroGold! With MetroGold you take your MetroGuide to the next level using all the functionality it can offer.

In Garmin MetroGuide, North America and Europe version, automatic route calculation is offered in the PC only. There is no route calculation data that can be transferred to a GPS even if it has autorouting capabilities. With MetroGold you can make your GPS capable of autorouting with MetroGuide maps. MetroGold will upgrade your MetroGuide to have this functionality. You can upload up to 4Gb of maps to your GPS.