I love to reuse candle jars, but dislike the task of cleaning out the old wax. I found this tip that might help you and me.
Put the used jar in the freezer, and a hour later, you can tap the bottom a few times and pop the wax right out.
Better yet,stick to tea lights. As long as the package says that the metal cups are aluminum, you can pull out the used wick and toss the metal in the recycling along with your cans.