There's quite a large difference between the two cities so we've put together a few tips to get you started.
Climate: Melbourne's weather is very different to Queensland. The winter's can get bitterly cold and wet. Ever wonder who actually buys the winter jackets and thermals in Queensland? Now you know.
Their summer can get and will get a lot hotter then the Gold Coast. Heatwave's reaching up to 40+ is not uncommon for a Melbourne summer, however they do not tend to last and can then drop from 40 down to 20 in a couple of days. Think "four seasons in one day". You will probably want to find a home with Aircon for these heatwave's. You will also need to invest in a heater or 3 for the winter.
City Size: Melbourne is a huge city with plenty of traffic. Melbourne has fantastic public transport in the form of trains, trams and buses. If you are needing to travel from outer suburbs into the CBD for work, you will probably want to seriously consider using the train to avoid being caught up in peak hour traffic.
Beaches: Melbourne does actually have swimming bay's and beaches and they are generally safe to swim at. Most beaches are patrolled by surf life saves during the summer months, school and public holiday and many are "no boat zones". There are however plenty of beautiful lakes around Victoria for you to go boating if you have decided to take your boat with you to Melbourne.
People: There is 4.5 million people living in Melbourne compared to just 600,000 on Gold Coast. So prepare yourself for a much faster paced lifestyle. Melbourne has previously been voted The Worlds Friendliest City, so you shouldn't have too many problems here.
Shopping: There is so much shopping....everywhere. With boutique fashion and homewares, Melbourne has a beautiful eclectic style that will have you finding one off pieces for your new home.
Food: Like shopping, food is everywhere you turn. From hole in the wall coffee shops to a massive range of international cuisine to choose from. You might want to join a gym.
Things to do: There is so much to do. Street art tours around the city as well as art exhibitions. Luna park. Festivals for everything. Days trips to Sovereign Hill (can even take the train) Phillip Island, The Dandenong's: Puffing Billy Steam Train, Mornington Peninsula: Red Hill Markets and Hot Springs and Yarra Valley Wineries to name just a few.