A down payment reduces the amount you need to borrow, which can save you money on interest payments over the life of the loan. It also starts you on a path to building equity in the home.
Look at the big picture of your finances before you make a down payment. You may want to keep cash in reserve to pay for unforeseen expenses or emergency repairs. If you have high interest debt, it may make more sense to pay down this debt rather than to put cash down on your house.