Transcranial magnetic stimulation (TMS) is a non-invasive method of brain stimulation that is receiving increasingly attention for new clinical applications. Through electromagnetic induction cortical activity can be modulated and therapeutic effects can be achieved in a variety of psychiatric and neurological conditions. According to the World Health Organization (WHO) depression is the most disabling disease in the world and 350 million people suffer from depression globally. Major depression is the most common disorder to be treated with TMS and the first mental disorder for which TMS received approval from the US Food and Drug Administration (FDA). We here introduce the basic principles of TMS, discuss the latest data on safety and side effects, and present various TMS treatment protocols as well as treatment response predictors in major depressive disorder.