Suppose the 2s and 2p orbitals of Lithium are on the same energy coordinate of Density of states graph with 4s and 4p orbitals of a transition series metal with a good number of population, will they hybridise?
Yes, they will. In the "natural" LCAO (tight-binding) description you can see how this depends on the relative position of the two atoms. I enclose two pages from a lecture in pdf format for clarity. I hope this helps!