Neither F2 nor Br2 are polar because they are nonpolar. It is a good rule of thumb to know that any diatomic molecules like F2 or Br2 are always going to be nonpolar. Another way to determine this is to use the acronym SNAP ( symmetrical=nonpolar, asymmetrical=polar). Since both F2 and Br2 are symmetrical molecules, they must be nonpolar.
I hope this helps.