Mechanical metamaterials are a category of artificial structural materials and essentially composite structures constructed with artificial microstructure units

which aim to enhance mechanical properties of macroscopic overall structure by designing the shape

size and periodic arrangement mode of artificial microstructure units

and to achieve extraordinary mechanical properties such as negative Poisson’s ratio

multi-stability

lightweight and high strength

and programmability/reprogrammability. However

mechanical metamaterials fabricated by conventional materials are difficult to meet the performance requirements of multi-environmental field adaptability

rapid and controllable environmental response

and energy conversion for functional devices in different engineering application scenarios. Mechanically functional metamaterials constructed by combining mechanical metamaterials with advanced functional materials expand the performance of mechanical metamaterials from the material perspective

and can achieve tunable electro-mechanical

magneto-mechanical and thermo-mechanical coupling responses

which are expected to realize the multifunctional engineering applications of mechanical metamaterials. This review describes the extraordinary mechanical properties and typical classifications of mechanical metamaterials

detailly introduce the construction methods and coupling responses of three representative mechanically functional metamaterials

namely electro-mechanical

magnetomechanical and thermo-mechanical metamaterials

and summarizes and prospects the potential engineering applications of mechanically functional metamaterials in the fields of aerospace and marine engineering

including self-folding satellite solar wings

micro-spacecraft self-powered

satellite platform vibration isolation

marine engineering and equipment monitoring and sensing

and marine wave energy harvesting.