what is sonorous?
Sonority is the property of a substance to produce sound when collide together. Metals are sonorous and produce sound when struck together in solid state.
Electron bonding in metals is highly delocalized, due to their very low electronegativity. This means that when struck, the electron cloud moves extremely easily - there is very little energy dissipated. This allows the incoming kinetic energy to be easily propagated as a form of disequilibrium - a wave.
Now, it should be noted that this is not in all metals - it is in sheet metals, and they have to be of relatively low density. High-density metals will not as easily propagate the kinetic energy, due to additional atomic collisions damping the effect.