I just got pulled over for both of my tail lights being out, and he said that it might be an electrical problem. I recently put in a new head unit without using a wire harness, so I just directly wired it to the wires going to the battery and stuff. Could that have been what caused the problem? Or could just both the tail lights coincidentally gone out at the same time? Or something else maybe?

 

The circuit boards inside the taillamp assembly tend to develop faults on your generation Malibu. Also, you could've blown a fuse or two while working on your radio. By "tail lights," do you mean the parking lights or stop lights? If they are stop lights, does the center high mounted stop lamp work? Have you checked the appropriate fuse (15A Park Lamps fuse in the underhood fuse block or 15A Stop Lamps fuse in the left I/P fuse block)? Do the hazard lights and turn signals work?