Question

A particle has more than enough energy to eject an electron from a metal's surface. What happens to the excess energy?

Answer 1

The electron moves away with the excess energy as kinetic energy.

Explanation:

We use this property in analysis of samples. I have done so myself at my job.

In energy dispersive X-1ray spectroscopy, we hit a sample with X rays that have more than enough energy to knock out inner shell electrons. The excess energy of the electrons is measured and compared with the energy of the incoming X rays, the difference is the binding energy of the inner shell electrons and thus identifies the element each electron came from. See https://en.wikipedia.org/wiki/Energy-dispersive_X-ray_spectroscopy.