Metro 2033 requires over 4 TFLOPS of graphics performance to play with maximum graphics at 1920×1080 and maintaining 60fps. See the page on game performance.
SETTINGS: DX11, Very High, 4x MSAA, 16X AF, PhysX, Advanced DOF, Tessellation
COMPARATIVE GPU PERFORMANCE CHART
See the page that features a graph of the relative performance of video cards.