Attached is pictures of my HVAC plenum, where it meets the ceiling.
Recently I had water damage(from upstairs neighbor) and I had to replace entire ceiling. After new ceiling I see this gap (yellow arrow) between this metal piece and the ceiling.
Any idea what is the purpose of this metal piece (blue arrows) ? If it is just to hide the gap between ceiling and HVAC duct, can I remove it and seal the gap with something else (may be some expandable foam covered by foil tape ) ?
If it is to hide the gap, I can unscrew and make it flush with ceiling but I will have to drill new holes in HVAC plenum which I don't want to do.