Given that the shape of the monument is a right pyramid with a regular hexagon as base.
The sides ot the pyramid consist of iscoseles triangles with base 5 meters and height 30 meters.
Area of each triangular side is given by

square meters
Area of the 6 triangular sides = 6 x 75 = 450 square meters.
Therefore, 450 square meters of metal is needed to cover the sides of the pyramid.