roof grounding

[Hunt Stoddard]

Does anyone know whether/how you are supposed to electrically ground metal roofs? This is for an 80s era pieced together house, off-grid, that has a pieced together 80s era solar PV system on the roof. Apparently it might have been lightning struck over New Years and there were discharges within it. Not sure if that's what happened, but the owner is now wondering about grounding.