Metallic Rattling Noise When ICE Under Load

Hi all, I recently purchased an 08 Prius with 115k miles. When the ICE is running under load (charging battery or first minute or so during a cold start) there's a metallic rattling noise coming from underneath the car. Does anyone know what would cause this?

Here's a video of the sound (at 0:56 the noise goes away):

 

Oil level was fine when I bought it. I've changed the oil and it sounds the same. It happens during cold start but I think it may happen anytime the engine is under load such as the hybrid battery charging but I'd have to check to be sure. I recorded another video. This noise isn't really audible until I go under the car at 0:20

 

No, according to carfax it had 89k miles in early 2025 so if anything it jumped in miles.

 

Looked under the car today since I had P0420 and a strong exhaust smell. I found two exhaust leaks - one at the exhaust donut and another where the back of the catalytic converter connects. I also found a few rocks on a bracket near the catalytic converter (didn't take a photo but I think it was unrelated). I watched a few videos of gen 2 cold starts and I think I hear the same sound as my car it just seems to be quieter so maybe the exhaust leak is making it louder?