The ornamental design for metal sheet, as shown and described.
FIG. 1 is a perspective view of a metal sheet showing my new design;
FIG. 2 is a front view thereof; the opposite side being a mirror image of the shown;
FIG. 3 is a right view thereof; the opposite side being a mirror image of the shown;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof; and,
FIG. 6 is the perspective view embodying the utilization of metal sheet in which the broken line is for illustrative purposes only and forms no part of the claimed design.