GoGoGadgetFusion had the solution for my rattle noise, it was the shocks. Took me ten minutes to fix. I have a 2013 Fusion Hybrid with +70K miles. The rattles started 3 months ago in the rear passenger side and then recently on the rear driver's side.
Fix was pretty easy.
Leave the tires on (its a little tight working space, but you don't have to jack up car or take off tire)
Spray the top bolt of the shock mast shaft with some penetrating oil
Put 15mm box wrench on mast nut
clamp on vice grip wrench to top of mast
Tighten nut (I was one able to tighten less than 1/8 turn)
Done
Drove car around the block and noise was gone. Hopefully it's a long term fix.