The OPERA experiment at the Gran Sasso underground laboratory has been designed to study the νμ→ντ oscillation in appearance mode in the CNGS neutrino beam.
The efforts of the Collaboration to extend the analysed data sample, with five identified ντ candidates overall, and to improve the knowledge of the expected background allowed to establish the discovery of νμ→ντ oscillation with a significance larger than 5 σ. In this talk, the ντ data analysis will be discussed, with emphasis on the background constraints obtained by using dedicated data-driven control samples. The analysis of the present τ neutrino and electron neutrino samples in the framework of the 3+1 sterile model will be presented. Finally the analysis of the muon charge ratio in the cosmic ray sample will be covered.