Metasurfaces are two-dimensional structures that can control the amplitude, phase and polarization of light in reflection or transmission. This allows metasurfaces to behave like traditional optical elements such as lenses, collimators or beamsplitters.  However, metasurfaces only work under very specific conditions and have a fixed optical response. In this work, we demonstrate tunable metasurfaces by utilizing the insulator-to-metal phase transition of vanadium dioxide (VO₂).  This transition allows a metasurface to have a large variety of behavior that depend on the temperature of VO₂.  Due to metasurface’s dependence on the spatial arrangement and properties of its unit cells, these tunable metasurfaces must be designed to function at both the insulating and metallic phase of VO₂. Using Finite-Difference Time-Domain (FDTD) simulation software and analytical electromagnetic techniques, we design and investigate the optical response of metasurfaces and thin-film stacks with a layer of VO₂. We successfully designed a tunable thin-film stack that modulates reflection. Additionally, it can function as a switchable polarizer. These results form the basis for designing more complex nano-optical components, such as reconfigurable gratings and tunable absorbers.