I get a rattle from what sounds like catylic converter area.

Wait for it to cool down, then gently attack it with a rubber hammer. Look for exhaust clamps that have rusted apart and are loose, and pound on the catalytic converter. They don't cause much trouble but there could be something loose inside that is rattling.

Some catalytic converters use little white beads, or pellets for the catalyst. Those aren't going to rattle and make noise. Older Fords and Chryslers used a porous rock. Those can break up, then the pieces can rattle. You'll hear it when you tap on the housing with a rubber hammer. This happened to my '88 Grand Caravan many years ago. The proper repair would have been to replace the converter if I wanted the noise gone. Since there was nothing to lose, I drilled a small hole in the bottom of the housing, then ran in a self-tapping screw with the sharp point ground off. I tightened it just enough for the rattle to stop. Over-tightening would likely have cracked the catalyst allowing the rattling to continue. That "fix" lasted well over 20 years and over 300,000 miles. The rattle never came back.