2010 - Tinny metallic rattle underneath?

I have a 2010 Forester, the heat shield is a POS. That is most likely your rattle.
Solution is to get about 6 to 10 hose clamps of various sizes (Amazon, stainless Steel) and crawl under there and hose clamp that rattling heat shield and the Catalytic converter shield too. It's a pain, I know.
My constant use in the salted roads of West Virginia and Virginia and the Pot holes of Washington, DC made my Forester extra noisy.

I'd second that, sounds very much like annoying heat shield rattle. Mine happens typically around 40mph while accelerating uphill. It's very intremittent but annoying. Usual fix is clamps and / or weging some screws in the looser areas.

Sounds like a pebble in a bake bean tin, right?!

It may not be this, but my sisters 2005 Forester had a strange metallic sounding rattle at low speeds and we couldn't find the source for the longest time. Turned out it was bad u-joints on the driveshaft. Something to check.

Thanks for answer ! Service dude tightened the screws which helped all of 10 minutes. Will see if my husband can crawl up under there . Thanks

excellent description !! Thanks

@spiritwof
You can just tear the whole thing off that’s why I did and no more rattle.