Bad rattling noise - need help

[Finny19]

So my car started making a weird noise today and i can't work out what it is.
When accelerating, there's a really awful metallic rattle that seems to happen around 1500 and 2500 rpm.
It also is constant if i change down a gear and let the car slow down by engine braking.

It sounds horrible and loud enough that pedestrians are starring at my car.
Any ideas what it could be???

[Lane]

Check all your engine mounts and exhaust brackets etc, could be something is loose and contacting something under tension/load.

[Finny19]

Loose O2 sensor in the front, was rattling around