The maturity date on your auto loan is the light at the end of the tunnel -- it's the date you are expected to make your final payment. After you make that final payment, no lien exists against the vehicle and your contract with the lender is satisfied.
The Final Payment
If you don't make that last payment on time, you can still default on the loan. Failure to make a payment can result in default whether you have one payment left or 36. When you near the maturity date, you can pay the loan off early if you like, but it's a good idea to call your lender for a payoff quote first. Paying the loan off early requires calculating any outstanding interest that's still unpaid. When your lender gives a payoff amount, it's usually accurate for about 10 days.
Leases Are Different
Leases have maturity dates, too, but you don't own the car after you reach this point. You have to give the vehicle back to the dealership so there's rarely any advantage in paying a lease off early unless you just want a new or different car. If this is the case, make sure you make all the payments before turning the car in. Otherwise, it could constitute an early termination of your lease agreement and you would typically be hit with extra fees which can sometimes be excessive.