The next morning after Mildred's overdose, Montag walks into the kitchen to see his wife happily eating breakfast. When Montag enters the kitchen, his futuristic toaster pops the toasted bread into the air and a mechanical hand grabs the piece of toast. The mechanical, spidery metal hand seizes the toast and drenches it with butter before placing it onto a plate. The mechanically advanced toaster is a minor object that contributes to the futuristic setting of the story. Bradbury's novel is a work of science fiction and is set in the futuristic United States, which is a technologically advanced dystopian society. In Bradbury's futuristic dystopian society, advanced mechanisms like the toaster and green bullet contribute to the setting. In addition to the technologically advanced toaster, the Mechanical Hound is another piece of advanced technology that enhances the setting.

You must remember that this is a science fiction book about the future.  The toaster is a combination of what we know today and some element of the future.  So, the person puts the bread in the toaster and it operates as it does in the present.  However, when it pops up, it is caught by a "spidery" metallic hand which butters it for you and then delivers it to your plate.  It does not explain how it knows where your plate is or what you do if you do not like butter, or if you want more than butter, like jam.  This is just a futuristic reference indicating to the reader that it is in a more technical society.