Scale the Machines
It was already known that Horizon Zero Dawn would allow you to take control of some of the machines that roam around the planet. Thanks to the footage at the PlayStation Event, we now know how that'll be going down, at least for the larger machines. In the trailer, Aloy climbs the creature's large body to get to its head and work her magic on it. It's likely that for more aggressive machines, they won't let you climb them without a fight.