Since Lars Leksell conceived of the Gamma Knife in the mid-20th century, it has become a fundamental strategy for managing intracranial tumors. The Gamma Knife harnesses around 200 focused beams of ionizing radiation that are directed stereotactically onto an intracranial target, destroying or inactivating it, all while sparing surrounding tissues. Today, a patient can have numerous intracranial tumors treated by radiosurgery in a minimally invasive fashion, during a single outpatient encounter, and return to usual activities the next day. Gamma Knife radiosurgery has found applications for nearly all intracranial tumors, either as a primary strategy or adjunctive therapy. In no area has Gamma Knife radiosurgery had a larger impact than in the treatment of brain metastases. In this article, we review the evolution of Gamma Knife radiosurgery, discuss current indications for the treatment of intracranial tumors and highlight how the future treatment of metastatic brain cancer may change.