Metamaterials are commonly associated to antennas and other microwave devices due to their unique ability to manipulate electromagnetic waves. In general, the approach used to select metamaterials for a given application is based on a classical approach by extracting the scattering parameters to evaluate the material effective properties. In this paper, we address the problem of evaluation and analysis of a specific metamaterial, a chiral helix metamaterial through the use of two modal analysis Expansion Eigenmode Method and the Characteristic Mode Theory. An interaction of the chiral helix with Circular Polarized electromagnetic plane waves is studied. The modal net stored energy of the metamaterial is also calculated. A good agreement is obtained between the net stored energy calculated by the two methods for the chiral metamaterial. The effect of polarisation on the metamaterial is also highlighted by the modal analysis. These modal approaches applied to chiral metamaterials can be of interest for the design of circularly polarised metamaterial antennas.