It is generally not a good idea to put buttered bread in a toaster as it will melt and make a mess in your toaster that won’t be so easy to clean. This is if the toaster is a basic pop-up toaster. And that is the best-case scenario for this kind of toaster. The worst is the butter will scorch and potentially spark off an electric fire. If you must toast your bread when buttered, you’re well advised to use a toaster oven. With this kind of toaster, you can lay on the butter as thickly as you want, provided you put your toast on a tray that can collect the excess melted butter.