It's going to be a while until The Avengers: Age of Ultron hits theaters (as in two whole years) so it's a little too early to expect any teasers that give us a look at the actual movie. It hasn't even started filming yet! Attendees of Comic-Con did get a little glimpse at Ultron's signature helmet in a short teaser, but that was never made available to the public—until now, because it just leaked.
The teaser, which will probably be taken down soon, features close-up imagery of Ultron's helmet being created as voiceovers can be heard in the background. Running at about a minute long, it doesn't include anything more than Ultron's helmet and the title card of the film, but it's still something.
You can check out the teaser above, while it's still available. The Avengers: Age of Ultron will be released on May 1, 2015.