Why is silver such a good reflector of visible light? In everyday mirrors, silver is used on the back of glass as a reflector (because it is highly efficient in reflecting visible light). But what are the characteristic properties that make silver a great reflector of visible light but not other metals?
 A: Metals are often good reflectors because they have a free sea of electrons that can slosh around in response to an electric field. Another way of saying this is that the energy levels of each atom become overlapped and form wide bands of possible energy levels for an electron. Therefore electrons can absorb and then re-emit photons over a large range of energy levels and not just at certain discrete energy levels like other materials without the sea of electrons (glass for example).
Edit: I just saw you asked why is silver better than other metals? I think one of the main reasons it that it is somewhat resistant to corrosion and there are really nice ways to deposit silver on glass using chemical reactions: https://www.instructables.com/Make-Glass-Mirrors-With-Silver-Nitrate-Sugar-Am/
A: Silver is a metal . Metals have free electron on their surface ie cause metals are electropositive in nature . They form cations by loss of electrons .when photon is absorbed by mobile electron it gets threshold energy . The high energy state of electron is unstable  . At the same time nucleus also attracts electron.so electron emits energy.
Also other metals  too are  good reflectors of light .metals are lustrous , shiny .the shiny appearance of metals make them good reflectors of light . That is why they are used in making mirrors .Few exceptional cases are there but other than that metals are good reflectors.
Also due to being cost effective ie cheap aluminium is used in mirrors nowadays
