Accurate subgrid-scale turbulence models are needed to perform realistic numerical magnetohydrodynamic (MHD) simulations of the subsurface flows of the Sun. To perform large-eddy simulations (LES) of turbulent MHD flows, three unknown terms have to be modeled. As a first step, we propose to use {a priori} tests to measure the accuracy of various models proposed to predict the SGS term appearing in the transport equation of the filtered magnetic field. We then evaluate the SGS model accuracy in term of structural and functional performance, i.e. the model capacity to locally approximate the unknown term and to reproduce its energetic action, respectively. From our tests, it appears that a mixed model based on the scale-similarity model has better performance.