The goal of this clinical research study is to learn about a new therapy device called the Visualase® Thermal Therapy System (a device that uses a laser to kill tumor cells and is guided using magnetic resonance thermal imaging [MRTI]). The Visualase® Thermal Therapy System is used to treat metastatic brain tumors. Researchers want to find out if it is possible to use this new device in patients with metastatic brain tumor(s), each measuring 3 centimeters (cm) or smaller. The safety of the device will also be studied.