Abstract: I will talk about mod $p$ cohomology of metacyclic groups. A metacyclic group is an extension of a cyclic group by another cyclic group. Mod $p$ cohomology rings of metacyclic groups are computed by Huebschmann using homological perturbation theory. Homological perturbation theory allows one to explicitly construct projective resolutions in an inductive fashion. I will describe this method and possibly relate it to other methods existing in the literature.