The adhesion of vapor deposited Au and Pt thin films onto poly(methyl methacrylate) (PMMA) substrates can be significantly enhanced by either spin-casting or vapor-exposure to hydrohalocarbon solvents prior to metal deposition. X-ray photoelectron spectroscopy (XPS) and evolved gas analysis Fourier transform infrared spectroscopy detect residual halogenated solvent at the PMMA surface which chemically activates the surface. Density functional theory (DFT) calculations show that the solvent molecules form a Lewis acid-base adduct with the ester oxygens in PMMA. DFT predicts that the deposited metal atom (M) inserts into the Chalogen (X) bond on either CHCl3 or CHBr3 to form a OMX interaction. This is consistent with MX bonding observed in high resolution XPS. A model is proposed in which the bond energy of the CX bond of the solvent must be weak enough so that it can be cleaved by the metal atom to form a MX bond. A negative control of PMMA exposed to CHF3 is shown to have no effect on Au or Pt adhesion since the bond dissociation energy of the CF bond is stronger than the CCl and CBr bond energy compared to the metal halide bond energies.