As seen from the point of view of effective properties, reinforced concrete is a metamaterial, with respect to mechanical properties. The original flavor of metamaterials was concerned with electromagnetic properties but it did not take long for people to generalize the ideas to a large panel of domains. Nowadays there are acoustical, thermal, mechanical, and even seismic metamaterials. This chapter presents a survey of these more unconventional propositions, together with experimental realizations. The emerging field of quantum metamaterials is also presented. The point there is to introduce quantum degrees of freedom in metamaterials, so as to obtain effective properties that depend on the quantum state of the basic elements constituting the metamaterial.