Among the highlights, collected by Collider, Singer says fans should expect a very different film from its other "X-Men" predecessors.
"Though there is a great deal of humor, the overall tone is a bit darker than previous films, particularly because of the stakes," Singer said. One of those stakes includes mutant-hunting robots the Sentinels, whose presence the director teased in a later tweet.
One Twitter user asked Singer if "Days of Future Past" would have a 1970s film vibe, since "X-Men: First Class" echoed the cinema 1960s. Singer confirmed that it would indeed invoke the disco era, specifically "in the colors, some of the style & music," and he also revealed that he used retro film to shoot several scenes.
For more from the director -- including scoop on Jennifer Lawrence's Mystique and a list of characters who'll be making their first "X-Men" appearance in "Days of Future Past" -- check out the full story at Collider.
The first trailer for "X-Men: Days of Future Past" is expected to drop Tuesday morning. The movie is due out in theaters May 23, 2014.