  Relevant studies of the non-thermal components of the intracluster medium are
performed at radio wavelengths. A number of clusters, indeed, exhibits
cluster-wide diffuse radio emission, which is indication of the existence of
large scale magnetic fields and of relativistic electrons in the cluster
volume. There is strong evidence that the presence of diffuse radio emission is
related to cluster merger processes. The details of the halo-merger connection
are discussed and a brief outline of current models of halo formation is
presented.
