  We examine the relevance of magneto-elastic coupling to describe the complex
magnetic and structural behaviour of the different classes of the iron
superconductors. We model the system as a two-dimensional metal whose magnetic
excitations interact with the distortions of the underlying square lattice.
Going beyond mean field we find that quantum fluctuation effects can explain
two unusual features of these materials that have attracted considerable
attention. First, why iron telluride orders magnetically at a non-nesting
wave-vector $(\pi/2, \pi/2)$ and not at the nesting wave-vector $(\pi, 0)$ as
in the iron arsenides, even though the nominal band structures of both these
systems are similar. And second, why the $(\pi, 0)$ magnetic transition in the
iron arsenides is often preceded by an orthorhombic structural transition.
These are robust properties of the model, independent of microscopic details,
and they emphasize the importance of the magneto-elastic interaction.
