The 28-year-old actress plays Queen Elizabeth I alongside Saoirse Ronan as Mary in the new drama movie, and Margot has revealed how her unflattering appearance in the film allowed her to empathise with the iconic British royal.
She told CNN: "It was really helpful, actually.
"The costumes too were very restrictive - you're wearing a corset and layer after layer ... I mean, there were jewels on your head, wigs, prosthetics for the pox mark scarring, and then of course really powdered make-up on top, which in Elizabeth's case had lead and arsenic in it ... in our case not so.
"But yeah, it was a lot and it felt very restrictive."
Margot claimed that her own sense of discomfort helped her to embody the character of the restrained monarch.
She said: "It was ironic and also helpful to feel trapped ultimately by the facade that she'd created for herself."
The Oscar-nominated actress has emerged as one of the most sought-after stars in Hollywood since her breakthrough performance in 'The Wolf of Wall Street' in 2013.
But Margot recently admitted she felt embarrassed shooting her most raunchy scene in 'The Wolf of Wall Street', in which she had to seduce her on-screen husband, played by Leonardo DiCaprio.
Reflecting on her experience of shooting the scene, Margot said: "It doesn't come across when you're watching the movie, but in reality we're in a tiny bedroom with 30 crew crammed in. All men.
"For 17 hours I'm pretending to be touching myself. It's just a very weird thing and you have to bury the embarrassment and the absurdity, really deep, and fully commit."