Social Security is an important part of the financial security of millions of Americans. But how does Social Security fit into your overall financial plan for retirement?

In the following segment from their video guide to investment planning, Motley Fool director of investment planning Dan Caplinger talks with Fool markets/IP bureau chief Mike Klesta about how to incorporate Social Security into a personal financial plan. Dan notes that while many retirees rely almost entirely on Social Security, it's far better to have Social Security make up just a portion of your financial resources, with retirement accounts and other savings playing a key role as well. Yet even though MetLife (NYSE:MET)Prudential (NYSE:PRU), and a host of other insurance companies offer annuities that provide some protection against running out of money, Social Security's most helpful attribute is that it provides lifelong income that never runs out. That makes Social Security a key aspect of your retirement security.