The only thing that runs through Steve’s mind as his eyes set on Tony is Oh no. Tony would say this isn’t an appropriate reaction to seeing one’s boyfriend, but really.
There’s no reason for him to be at the post-victory party in nothing but his underarmour. He should be in the armour or his normal clothes, not a perfectly fitting body-tight black fabric that leaves nothing to the imagination.
He looks at Steve through his lashes.
Apparently, he doesn’t want to attend his own party, Steve decides, grabbing him by his wrist to pull him into an empty room.