The goal of a résumé is to get you an interview but the goal of a cover letter is to get you the job?

No. The aim of both together is (1) to make you interesting to the employed and (2) get you an interview - obviously with a view to getting the job. Incidentally, the covering letter should usually be short, simply to make show the employer knows that you can be polite. Information about yourself should go in the resumé. Avoid long, shaggy dog letters like the plague!