We consider dynamics of a symmetron-like field to investigate dark matter effects on galaxy scales. For this purpose, we propose a model for the metric components of a spherically symmetric space–time in regions of galactic halos where the rotation curves are flat. Then, we show that the mass corresponding to the effects of the symmetron scalar field obtained from modified Einstein field equations is responsible for the flat rotation curves in a galactic halo so that the motion of test particles in such a region can be explained without the need to introduce dark matter. In addition, the light deflection angle for this model is investigated in a galactic halo as a possible physical test for comparison purposes. The results show compatibility with previous models such as generalized pseudo-isothermal dark matter with exponential matter density, brane F(R) or F(R, T ) gravity.
