my rear deck rattles like hell does anyone know how to fix it?

most people will yell at you to search because its been discussed 10 million times over.
basically the 2 main options you have are these:
1. get foam from walmart for stuffing toys and stuffit in between the sheet metal and teh rear deck cover.
2. buy sound dampener or deadener and put it on the sheet metal between the metal and the rear deck cover.

There are other options but these 2 are the most common. lates. and next time use the search function.