  We discuss Mott insulating and metallic phases of a model with $e_g$ orbital
degeneracy to understand physics of Mn perovskite compounds. Quantum Monte
Carlo and Lanczos diagonalization results are discussed in this model. To
reproduce experimental results on charge gap and Jahn-Teller distortions, we
show that a synergy between the strong correlation effects and the Jahn-Teller
coupling is important. The incoherent charge dynamics and strong charge
fluctuations are characteristic of the metallic phase accompanied with critical
enhancement of short-ranged orbital correlation near the insulator.
