Yes, you can absolutely put bread in a toaster without butter. The toaster is designed to toast bread slices to make them crispy and brown. Butter is an optional ingredient that some people like to spread on their toast after it's been toasted to add flavor and moisture.
Toasting bread without butter is a common practice, and many people enjoy plain, toasted bread with various toppings like jam, peanut butter, avocado, eggs, or just on its own. It all comes down to personal preference and dietary choices.
So feel free to put bread in a toaster without butter, and enjoy it as you like!