Sites and dynamics obtained for muonium (Mu) defect centres provide a good experimental model for the behaviour of the equivalent hydrogen impurities. We discuss the dynamic properties of Mu centres in the III-V nitrides focusing on features common to the three materials. Muon spin depolarization data in zero magnetic field provide motional dynamics for the Mu(+) and Mu(-) charge states and field dependent longitudinal relaxation rates probe motion of Mu(0) centres. The data also show dynamics associated with metastable locations, either intrinsic to the wurtzite structure or defect related, including trapping and release transitions. A general picture of the behaviour of H in the III-V nitrides is developed from these measurements for comparison to theoretical results.