  We study the dynamics of a pair of nonlinear split-ring resonators (a
`metadimer') excited by an alternating magnetic field and coupled magnetically.
Linear metadimers of this kind have been recently used as the elementary
components for three-dimensional metamaterials or 'stereometamaterials' [N. Liu
{\em et al}, Nature Photon. {\bf 3}, 157 (2009)]. We demonstrate that
nonlinearity offers more possibilities with respect to real-time tunability and
a multiplicity of states which can be reached by varying the external field.
Moreover, we demonstrate almost total localization of the energy in one of the
resonators in a broad range of parameters.
