A security element, such as a thread, strip and the like, for security documents in general, which comprises a flexible backing layer that has, on at least one face, a layer of metallic material provided with regions in which the thickness of the metal is less than 70% and more than 25% of the thickness of the layer of metallic material of the nearby portions, and further comprises a layer of embossed holographic lacquer between the backing layer and the layer of metallic material.