Jack Nance plays the central man Henry Spencer who inhabits a most bizarre world filled with some equally bizarre people and creatures. Henry is perhaps the least odd thing about the film which isn't saying a lot, I mean just look at his haircut after all. Nance's performance fulfills a very particular role in that he's the kinda sorta straight man to the rest of the film. Both the kinda and sorta are needed though because it's hard to say that Nance's portrayal of Henry is exactly how a normal guy would react in such a situation. Nance's performance is also very much in the way of Lynch's style, although still feels less of one of "freaks" like the way all the other performances are. Nance has an almost comic manner with his performance with the way he portrays a certain constant unease at all the oddness, which actually seems like a rather reasonable reaction to everything going on around him.
Nance's performance is mostly reactive altogether as there is not exactly a lot of scenes where we understand the inner workings of Henry as a man, well unless one is referring to what is below his head if it were to fall off. Nance's performance though does work in his limited role of reacting to the odd things whether it is his manic fiancee, his alluring neighbor, his horny potential future mother in law, his constantly crying and seemingly dying alien son, a bleeding turkey dinner, or all sorts of other odd things going on in this world. Nance's reactions tend to be effective in one way or another. The first being just reflective of the oddness itself and Nance does a fine job of giving at least an ever so slightly realistic reaction to these completely out there images. Although I won't say that Nance really makes the film seem believable so to speak but his performance in a somewhat strange way facilitates them as a more accessible whole.
Jack Nance's performance here is a good one that not only matches David Lynch's most unusual style, but helps to amplify. One of the last shots of the film of Henry staring out would not be nearly as remarkable if not for Nance's combination of fear and astonishment that he portrays in Henry's face. He is always interesting to say the least in every frame that he does inhabit. Nevertheless, having said that Nance's performance is very much a cog in David Lynch's machine as all the performances in the film are. Nance's performance stands out the most in terms of the cast, but when thinking about the film it is doubtful that one would necessarily remember Henry as a character so to speak. It is more likely one would remember the imagery and how Henry is part of that imagery. Nance serves his purpose as in the film well, but it is always the film as a whole, rather than Nance's work as a individual, that leaves the strongest impression.