The Flash will feature the return of Michael Keaton as his version of Bruce Wayne from the Tim Burton movies, and a new reveal through a line of toys shares more information on what role the older Batman will play in the DC movie. Keaton will don the cowl for the first time since he last played the role in 1992's Batman Returns. The Flash will present a multiverse story with Ezra Miller's Barry Allen that will see him travel to an alternate universe that is home to Keaton's Batman. However, the Dark Knight will be in very a different place than audiences last saw him.
https://screenrant.com/the-flash-movie-michael-keaton-batman-details/