“For the past week, director Michael Bay has been filming explosive battle scene for Transformers: The Last Knight in Bourne Woods (located south of Farnham, Surrey, England). The battle scene, as you can see in the set videos above and below, appears to be set in medieval times and features knights, dressed in full-armor, on horseback and off charging into battle.”

We’ll probably know more in November or December. That’s when the first teaser trailer will arrive, according to Bay.
Source: Comicbook.com