The invention relates to a metamaterial. The metamaterial is applicable to transmission of electromagnetic waves of a Ka waveband. The metamaterial comprises at least one metamaterial sheet layer, wherein the metamaterial sheet layer comprises a first dielectric substrate and a plurality of man-made microstructures which are arranged on the first dielectric substrate in an array mode, each man-made microstructure comprises four straight line sections which extend out from the same point and are the same in size, every two adjacent straight line sections are perpendicular to each other in the clockwise direction or the anticlockwise direction using the point as the central point, a gap is reserved between each straight line section of the corresponding man-made microstructure and one straight line section of each of other four adjacent man-made microstructures, and two corresponding straight line sections of every two adjacent man-made microstructures are arranged on the same straight line. The electromagnetic waves of the Ka waveband can efficiently penetrate through the metamaterial, loss is low, good wave permeability is achieved, the wave permeability rate in the Ka waveband is stable, and the metamaterial has the broadband characteristic. The invention further provides a metamaterial radome made of the metamaterial and an antenna system.