He likes to touch things.
The feel of something beneath his fingertips is all he knows of love. He can feel heat and chill, movement and stillness, can feel the thrum of someone's heart of the whirr of a machine. When he touches, he not only sees, but he feels, and it's as close as he can be to anything in the twenty-first century, the new world of light and sound and white noise- the future.
He likes the future because there are so many things to touch.
He finds that, despite what the media would have you believe, he loves the machines the most. Machines, he can understand. They have a code, a password, a rhyme and a reason- he may not understand the rhymes or follow the reasons, but they have one. They are carefully controlled chaos masked with sleek chromes and well-oiled cogs and they are electrifying beneath his already calloused fingertips- they sing, and beat, and shake with energy and he cannot bear to tear himself away from them, the numbers and the always solutions. He may not understand why he is here, or where here is, really, if he's feeling honest, or what Keeping Up With the Kardashians is, but he understands machines.
For all his understanding of machines, he understands Tony Stark the most.
He is built from a machine, that boy, came into the world with blinking eyes and nimble fingers and calculations. He could build before he could speak and does math so complex in his head it makes Steve's eyes whirl when he watches Tony- the taptaptap of his fingers on his thigh, the sharp twitch of his mouth, the small smile when he reaches the answer. He is surprisingly simple and yet oh-so complex; he moves like a machine and fights like a machine but he speaks like a human- erratic, short-breathed snarky comments accentuated with hatred in dark eyes, shaky breaths taken in the dark embrace of night when he sips from his drink and just trembles. To the untrained eye, Tony Stark is the epitome of mystery and confusion, ever unpredictable.
Steve's eyes are very, very trained.
He can take Tony apart and put him back together in different ways and the man always seems to fit there, like a permanent fixture destined to operate forever. He is sleek gold-titanium alloy and soft skin and rough teeth but he still feels like a machine, when you touch his chest, and Steve understands.
He understands the energy rolling from Tony in the darkness of night and the nervous bouncing in large groups of people, and the broken whispers that spill between gritted teeth in the night, the holes between canines punctured with I'm sorry and JARVIS, run suits specs at 75% and hold. He understands the desperate need for always noise and the banging of the drums, and the carefully released exhalations of breath when he's tucked into Steve's arm that tickle across his skin and sound like the word happiness. He understands machines, and rhyme, and controlled chaos, and it understands him.
(He comes to find out that Tony fucks like a machine, too; a calculated pattern of giving and taking and whirring and thought, a smooth sensation of constant rolling that is down to a science. He does not mind, because he can deal with machines. It's the other things, like breathing and press conferences and oh, look, you've been asleep for seventy years, that he cannot.)
He traces soft pictures of sunrises and bloody flags into Tony's skin with one finger, feeling the rough goosebumps beneath his touch that feels like metal. His tongue dances across the lines he makes, carving phrases like I love you and never leave and it all tastes so metallic and bittersweet that he cannot get enough of the machines, of Tony, of touch.
(He needs to feel the pulse racing beneath warm cells to know he's alive, too.)
And when he touches Tony, he touches the machine. The machine that he can understand and define; if you adjust the numbers, eventually it will crack. The machine does not desert him, and the machine does not lie.
It does not say foolish notions like the world has not changed all that much, Rogers, or false reassurances like with time, you'll understand it all. It's just culture shock.
It does not ask him to understand so he understands anyway; out of spite, perhaps, but maybe out of basic need. Tony never flinches or breaks; he is sturdy, like gold-titanium alloy, like vibranium, like Steve needs him to be. He never takes more than he can give and never breaks anything he shouldn't and when he whispers equations and numbers into Steve's neck when they fuck, gentle and slow, he doesn't try to hide them. Tony moves like the machine so he feels like one, sounds like one, but is so gentle and warm and does not mind a man who cannot tell you the last five presidents or a man who is drowning in seventy years of tears. He sits and thinks and calculates and offers his body, his mind, his eyes to Steve, who drinks them in like he hasn't drank in a century and he understands this kind of machine.
And then he simply touches.