Why does my Ford Focus's engine make a rattling sound?

I have a 2019 Ford Focus and lately it has been making a rattling sound, especially when I start the car. What could be causing this and how can I fix it?

The rattling sound could be caused by a loose exhaust manifold heat shield. It is recommended to have a mechanic take a look and tighten any loose bolts.

I had the same issue with my 2018 Ford Focus and it turned out to be a faulty belt tensioner. I would suggest getting it checked out by a mechanic before it causes any further damage.