Jessica Chastain has joked she will make James McAvoy cry ''so hard'' on the set of 'X-Men: Dark Phoenix'.

The flame-haired actress stars alongside James in the new superhero movie and while she's remained tight-lipped about her character's identity, Jessica has suggested she will play an important, villainous role.

Alongside a picture of herself and James on her Instagram account, the 40-year-old star wrote: ''Hey @jamesmcavoyrealdeal you ready for me up in Montreal? Im gonna make you cry so hard (sic)''

Jessica recently admitted she loves sharing things with her fans on social media - although she is still slightly guarded about what she posts on sites like Instagram.

The Hollywood actress explained she enjoys maintaining an ''air of mystery'' about herself.

She said: ''I love sharing things with my fans and social media is a fantastic platform to put [positive things into the world].

''I don't put anything out there that isn't already in the press. I'm not going to put a picture of myself in a bikini.

''I'm not going to put a picture of something people wouldn't normally see. I like to keep an air of mystery.''

And despite being one of the most sought-after women in the movie business, Jessica confessed that she doesn't feel ''uber confident''.

She said: ''It's not an industry that creates confidence; it's something you've really got to find within yourself.

''I don't feel uber-confident.''

Jessica also said she is a ''very awkward girl'' and can be unsociable at times.

Jessica shared: ''I'm actually normally a very awkward girl and kind of shy and I'm not very social and so much has been going on. I'm talking about gender politics and the wage gap and women not asking for what they need.''