Why Do Flame Tests Only Identify Metals?

[chemist2b]

Flame tests are used to test the color that a metal produces when heated and the electrons release energy when falling back to the ground state. This i understand, but why does the procedure only test the metal part of the salt? In other words, why does the anion part of the ionic compound not effect the flame color?

 

[Borek]

In theory it could, it just happens that most anions don't emit visible light. I doubt it is more than just a coincidence.