We know that protons and neutrons, which make the nucleus of an atom, are made of quarks. Interaction between the quarks is mediated via the gluons. Quantum Chromodynamics (QCD) is the theory that describes this interaction using field theory techniques. Although this theory was proposed almost 50 years ago, there are still some open questions in this field. Mesons are one of the predictions of QCD  that we observe in the detectors, which enables us to study some of the properties of QCD effectively. This talk will cover our works on mesons with higher spin and instanton effect on them.