Bruce Wayne likes masks
He doesn't like all the lying but he doesn't know how to live without the faces he created. He likes masks because they offer protection. Nobody can hurt you if they don't know who you are. Not really. And Bruce has been hurt enough. Bruce doesn't show anybody his true face and after a while he stops believing he has one worth seeing. Masks are simple. Then along came tony stark. A man who sees behind the too wide smiles and threatening voice, someone who sees behind the lies that cover Bruces life. He doesn't know why tony cares. Bruce likes masks because without them he doesn't know who he's supposed to be. He doesn't know how to act. It takes a while for tony to show him that even the best actors take a break occasionally.
Bruce Wayne likes training
He likes the distraction it provides from his work and his responsibilities. When he trains it is easy to forget everything that's happened, everything that could happen. Bruce has pushed himself to the edges of physical endurance but he still feels the need to go further.
It had been a bad night. The joker escaped again and killed six people before the batman caught him. Bruce is covered in sweat and blood. His muscles scream in protest as he loses himself in the rhythm of push ups. He's exhausted but he doesn't stop. He can't stop. He needs to be better, to be faster. After his knuckles are bleeding and his stitches have begun to reopen, Bruce feels arms force him to stop, feels himself collapse to the ground. When he's pulled to his feet and guided to a chair, he doesn't protest. Bruce often pushes himself as far as it's possible for him to go but sometimes he appreciates it when a friend tries to hold him back.
Bruce wayne likes shadows
And the shadows love him. The night embraces its guardian and hides him from the prey he stalks in the alleys. Bruce likes the shadows because they are dangerous and threatening. They terrify the criminals because the criminals know what lurks in them. The Gotham underworld knows to fear the dark because now the darkness fights back. Bruce is sure he'll hate Malibu, the bright lights and loud parties irritate him. It's nothing like his home and he considers being there a waste of time. Bruce doesn't like being away from his cave but while sitting in Tonys workshop, fiddling with wires and blueprints, he thinks that perhaps it's ok sometimes to leave the shadows. If only for a little while.
Bruce Wayne likes science
He likes the patterns that are always present if you look close enough. He likes how all the numbers and equations add up to answers. In chemistry every action will have a reaction and usually you know what it will be. People are often like that. If you study them long enough and Watch them close enough you can predict their every action, every movement. That makes it easy to know what they want. Except sometimes someone comes along that doesn't react the way they should. Sometimes despite the conditions, the measurements and the many calculations people can surprise you. That's partly why he enjoys being with tony stark. Tony never does as Bruce expects, he never acts the way the calculations say he should. Bruce likes science but occasionally it's nice not knowing all the answers.
Bruce Wayne likes scars
They're a reminder of his failures, of his weakness. The black and blue bruises that cover his skin are ugly and menacing but he's glad they're there. They are evidence that no matter how strong or smart or fast you are, it will never be good enough. You can always achieve more. Be more. Bruce Wayne knows that the scars that cover his skin like gruesome brush marks on a canvas are hideous but he doesn't care. Bruce Wayne is broken and it seems only right that his skin resembles what he knows to be true about himself. The night he kisses Tony Stark, Bruce realises that being broken doesn't mean you can't be fixed and nor does it mean you should be. When Bruce kisses tony for the first time, he realises that scars can be beautiful.
Bruce Wayne loves tony stark
He knows he shouldn't. Love is dangerous. If experience has shown Bruce anything, it's that love can never be trusted because in the end it will fail and the one you care for will leave you or be taken. He nearly says the words many times but then he remembers that it will not last. He remembers that he can't afford distractions from his mission. He can't afford to let himself be completely happy. Bruce Wayne often thinks of how bad love is but when he wakes up in the morning, after a long night of patrol, to see his lover asleep on the bed next to him, The arc reactor throwing shadows over his face, Bruce can't bring himself to care. They're together for now and that's enough.