a metal rattle from the front in any minor or major bump

I have a 2010 Mazda 3i Touring sedan (with manual transmission). I have a metalic rattle coming from the right rear of the car. After a number of visits to the dealer (including rear shock replacement), the problem turned out to be loose splash guard within the fuel tank. This seems to be a problem endemic to all of the newer models. Replacing it with another tank won't help since they all have this problem. Hope this helps for what it is worth.

Check the upper bracket of front struts. The center upper bolt hole of this bracket gets bigger if the strut nut gets loose. therefore the struts move slightly making that noise at low speeds.