Hey,
This isn't anything to worry about as nothing seems broken. The plastic piece is the center cap to the alloy wheels, while the metal ring is just a snap ring or retaining ring clip (can't exactly tell) to support holding the plastic piece. It seems like it came loose from a bump or something and had been spinning around making noise. Put the center cap back on and make sure the ring is securely attached. If the noise persists, there may be a possibility that something is broken. If so, reply, let me know, I'll try to find a replacement part or any other information.
Good Luck.