Ceramic vs. Film Capacitor: Which one is preferred in audio circuits?
"Film Capacitor" typically denotes polyester or polymer film as the dielectric - as another answer points out, metallized film capacitors are the same thing: A metallic coating being applied to an extremely thin polymer film, to create the conducting electrodes of the capacitor.

In general, ceramic capacitors are somewhat non-linear in their frequency and voltage responses, compared to film capacitors. Another issue with ceramic capacitors is that they tend to behave as microphones, thus picking up ambient sound and modulating the voltage across them accordingly.

Also, for smaller values (a few pF), ceramics were more commonly used, while larger values were somewhat  likely to have film considered as an option - or at least that was how it used to be, before capacitors became so inexpensive with the advent of SMT, that the price difference became negligible except for huge volumes. 

Both film caps and ceramic ones are non-polarized, so that isn't a difference.