Mechanical metamaterials can achieve unusual material properties that cannot be captured in standard materials, such as negative Poisson's ratio. These materials show exotic properties, for example, large deformations in shape (without failure), programmable stiffness change, and energy dissipation under mechanical loading. In order to capture those exotic material properties, metamaterials should be designed accordingly. In this short work, I wanted to show, different kinds of metamaterial designs and their instabilities under mechanical loadings. Compression tests are conducted in quasi-static test conditions (10 mm/min speed, 0.005 s-1 strain rate). TPU (thermoplastic polyurethane) is used in the 3D printing of the designs.