ABSTRACT A metamaterial (MM) is an artificial material with an internal micro-structure designed to achieve target properties of any type: structural, optical, acoustic absorption, etc. MMs possess an internal micro-structure of certain complexity, whose design drives the aimed properties at macro level [1]. A classical structural MM is a honeycomb sandwich panel, often used in aero-space applications to achieve high stiffness and high strength, and low weight. Another example are the so called Auxetic MMs that present an unconventional mechanical behaviour: a negative Poisson´s ratio. This unconventional behaviour is interesting for many applications such as impact energy absorption, and improved fatigue and fracture mechanics properties. The structural simulation of MMs is of certain difficulty because it has to consider both the analysis of the internal structure (the micro-structure responsible of the desired properties), and the analysis of the macro-structure itself: a box, a reinforced structure, etc. A technique quite often used is the multi-scale Finite Element Analysis (FEA), but when the structure undergoes large strains MM multiscale FEA becomes prohibitive in computational cost. The paper proposed an efficient procedure for multiscale MM FEA, the micro-level structural properties of the structure are found through Virtual Tests of a representative volume (RV) of the MM, considering different deformation modes, and all possible combinations. These micro-level behaviour is recovered in different constitutive phenomenological curves that are used by a macro FE tool developed at the ETSIAE (UPM): WYPiWYG [2]. WYPiWYG is based in a hyperelastic material constitutive model, and currently it may deal with isotropic and orthotropic (incompressible or compressible) material behaviours, at both infinitesimal and finite strains. Under these constraints, the tool shows a high efficiency and high accuracy. REFERENCES [1] Bishop-Moser J., Spadaccini, C., Andres C., Metamaterials Manufacturing, Pathway to Industrial Competitiveness, MForesight (Alliance for Manufacturing Foresight) Report, 2018. [2] Amores V.J., San Millán F.J., Ben-Yelun I., Montáns F.J., A finite strain non-parametric hyperelastic extension of the classical phenomenological theory for orthotropic compressible composites, Composites Part B: Engineering, Vol. 212 (2021), 108591.