This film has very good cinematography, interesting and compelling images, very realistic language (both American English--spoken by Scarlett Johansson--and English spoken by Glasgow natives in Scotland). In fact, one thing this film lacked was subtitles. Too bad. It needed them. The English spoken by the Scots was completely incomprehensible to American ears.
Now, that didn't ruin the film by any means. The weight of the entire film is carried on the images. Scarlett Johansson plays an extra-terrestrial who "takes the skin and bodily features" (or rather, the very beautiful and shapely bod) of a dead motocyclist (Johansson), and then drives through cities and towns attracting men to her van. They get in, one after another after she stops for them on the street, and they follow her into buildings where she strips off one by one pieces of clothing and they, lusting after the beautiful form, then follow on till they sink into a liquid. The darkness of the liquid, the beautiful figure of a woman, the desire of the men so great they'll die to have sex with her-- all these a very compelling and gripping. It is true. Men can be like that in their desire.
But for a "study" of gender roles-- no. This film's power lies in its images, not in its profundity. At the end of the film, the Extra-Terrestrial is raped. That is, a man in a forest tries to rape her, rips of the skin, sees the alien beneath the skin, and throws gasoline on her and burns her to death.
That the alien has only assumed the lineaments of a sexed human being is the message, I guess. We're all "the same under the skin?" Is that it? Well, too bad. I don't believe that we are. We are this or that, truly, and everything else is guesswork. We are men or we are women or we are transgendered, or terribly macho men, but we are particular and not general, we are one or the other, tough luck.
I don't much like Allegories, and this had me allegorizing all the time, fitting the puzzles together. When the Extra-Terrestrial instead of drowning the "ugly man" in his desire, takes pity on him and lets him live, then Wunderbar! I thought "Great. The movie has taken a turn that I recognize and now is going to develop!" But no, after that more allegorizing.
The Sci-Fi was only a "frame" for the film. The substance of the film is sex and gender. We're so very familiar with those, it was pretty bored--except by the wonderful imagery and pitiful fate of the men who followed their desire, my brothers under the skin. I, too, would have followed that shapely phantom into a dark building...