I want to make a small car, use the driver module, and there is just one piece of ULN2003 on hand (this is: http://www.omo-ic.com/chip/c69/ULN2003A.html), I think if I can use This chip is used to drive, check DATASHEET, the current of each port is 500mA, I use two ports in parallel to control one motor in one port, a total of 4 ports control 2 motors, the battery uses two sections 3.7 lithium battery, I don't know if this chip can work very well.
There are two reasons why this may not work.
Although each channel can sink 500mA in isolation, the chip cannot sink much more than this in total. It would quickly overheat and fail. Even small motors can require large current for a short time when they start up. You need to measure the "Stall current" of your motors.
ULN2003 channels can only sink current. They cannot source it. If you motors only run in forward direction and never reverse direction, then ULN will work for that. But if you need forward and reverse, the ULN is not suitable, you need to build an "H-bridge" and ULN cannot do this by itself. Maybe if you have some pnp transistors or p-channel mosfets, you can use these combined with ULN to build an H-bridge.
Sounds like you need an H-bridge.