what mode is a song in if the melody hits the 5 a lot but the chord progression resolves to the 1. like a song in F's melody being based around C but the progression resolves to F major.
if you're not sure about the 'mode' then you might not be sure about what key it's in either. without hearing it, i'm not sure, but something tells me you are hearing a song in C that leads with the F chord every time