Events containing muons in the final state are important for many physics analyses being carried out at the Large Hadron Collider, including both Standard Model measurements and searches for new physics. The muon trigger in the ATLAS experiment consists of a hardware-based first level trigger, and a succeeding software-based trigger. In order to handle the high luminosity in Run-2, several upgrades have been implemented to reduce trigger rate, while keeping a high efficiency. These improvements have been done by coincidence of hits in the muon spectrometer and the calorimeter, optimisation of muon isolation, and better determination of transverse momentum. An overview of the muon trigger in ATLAS with the recent improvements is presented. Also performance of the muon trigger in Run-2 and an outlook for upgrades planned for Run-3 are presented.