If you heat the metal, the electrons will come out more easily. Actually, you don't even have to irradiate: if you apply enough potential, you can pull electrons out of a metal. Now if you attach a negative electrode to the metal and a positive electrode close to the surface, you can push/pull that electron (or one other from the sea of electrons) off - the application of a potential gives KE to a free electron. The observable effect will be that irradiation with this wavelength warms the metal as much as possible without exciting any electrons to the 'outside' world.
Then, after a while, an electron drops in around that nucleus, giving a bit of (thermal) shock.
If you irradiate a metal with the exact amount of energy to produce a free electron with KE = 0, it will just stay free, in the 'sea of electrons' of the metal, while the nucleus, with its positive charge, also sits in the same sea - near 'other' electrons, each of which has KE due to temperature.
