A/N: This is inspired by a headcanon submitted imaginebucky on tumblr.
"Imagine Bucky's metal arm whirring and clicking when he's about to have a panic attack or when he's very stressed so Steve and/or Sam know when to try to talk him through things. On the flip side, imagine Bucky's arm faintly buzzing, almost purring when he's warm and relaxed."
And this is where the story went for me…
It's become part of their routine.
Some days they run in the National Mall, passing the monuments and scattering sleepy birds. Other days they run through Embassy Row, or just wherever they feel like that morning.
They run side by side for a while until Steve has warmed up, pulling ahead of Sam, his dark blue shoes thudding against the pavement in a steady rhythm.
"On your left," Steve passes Sam, and after a few minutes later, again "On your left."
Sam rolls his eyes, but doesn't change his pace.
Afterwards they go back to Sam's place for breakfast; sometimes Steve makes waffles or pancakes, other times Sam makes omelets. Later they go to their day jobs- Steve to SHIELD HQ, Sam to help with his group.
This time is different, their routine is interrupted.