Oops yes metal bar was a bad choice as the battery live is connected directly to the starter motor, hence the advice to use a wooden tool. At least it was only a small spark and you are up and running. However it kind of confirms that your starter motor is sticking, a common problem. It does need replaced or at least stripped, cleaned and lubricated properly, and yes sodds law says that it will fail on you at the worst possible moment.
Dont know the exact location of the starter motor or your mechanical ability but needs dealt with sooner rather than later, but remember ALWAYS DISCONNECT THE BATTERY BEFORE working on the starter motor or anything electrical for that matter. Make sure you have the code for your radio if it has one before disconnecting the battery though or that will be your next problem.
Good Luck
B, September 2008