ergers between galaxy clusters are the most energetic phenomena in the Universe. During these cosmic collisions, turbulence and shocks are generated into the ICM where they are believed to power Mpc-scale diffuse sources called radio halos and radio relics. LOFAR is a revolutionary radio telescope that is opening a new observational window at low frequency and that is expected to increase our knowledge of non-thermal phenomena in galaxy clusters. I will present LOFAR observations at 150 MHz of A1758 and A781, two merging galaxy clusters in a complex dynamical state, known to host evidence of diffuse radio emissions in the ICM. LOFAR allows to study with greater detail these steep spectrum sources recovering more (and new) diffuse emission in the clusters. I will conclude my talk describing a recent work devoted to the search for X-ray discontinuities with Chandra in merging galaxy clusters. In particular, the detection of new shocks is important to consolidate the relic-shock connection.