I found a broken tab of a shingle on my front lawn today. As far as I can tell, it came from the area of my roof that I've attached a picture of here. I was thinking that the roofers may have taken a tab from a shingle and glued it over the metal piece. Is the metal I'm seeing flashing? I've never done roofing work before, so I want to make sure I understand what's wrong (if anything).

Wasn't sure if I should I get a replacement tab and glue it on top of that metal piece, or get a full shingle, remove the nails from the surrounding shingles and get the full replacement in there, or do nothing. Based on the black residue I see on the metal, I'm assuming the tab I found today must have been on top of that piece of metal. I wasn't sure if it's okay for the metal to be exposed like that. We had very windy weather lately, so I'm guessing the shingle I found was on top of that metal and flew off (as I don't see any other area of my roof missing a shingle).