Yes, you can, but it should not be heavy. The general rule of what to put on your refrigerator can be measured by your arms. A refrigerator is a solid appliance; hence it can bear some weight. To measure how much weight you can put over it, just lift an object above your head, and if you can, then no problem in placing them on the refrigerator.However, ensure that the base of your fridge is stable and the object doesn’t block airflow around it. Additionally, you should remember that the things on top of the fridge might get hot; hence be careful when placing any item over your fridge.