Peter Bogdonavich remarks in the introduction to his interview with Fritz Lang that when Alfred Hitchcock was first gaining esteem, he was deemed the British Fritz Lang. When Lang's fortunes waned, Bogdonavich remarks, he would come to be called the German Alfred Hitchcock.
Indeed, in M we see many techniques employed that would go on to be hallmarks of Hitchcock's films. Most notable is that sequence when Hans Beckert is being pursued by the street person tipped off the blind vendor. Lang makes expert use of cross cutting to stretch out time and enact a series of reversals between who is the hunter and who is the hunted.
There's even that consummately Hitchcockian (or, Langian, really) series of shots where Beckert pulls out his glistening knife, only to use it to cut up a piece of fruit. Yet, while he uses that knife quite differently than we may have predicted, there's something so sultry and violent about the way it cuts into the fruit's soft flesh, something so terrifying about how adeptly Beckert carves. Lang even beats Hitchcock to the punch on Hitchcock's own tendency to make shots suggesting violence the most titillating.
So much of Hitchcock's visual style in his black-and-white films revolves around the play of light and shadow. The shadow of the murderer during that infamous shower scene in Psycho? See it in M first when the child murderer's shadow first appears over a poster telling his own crimes, as he engages the innocent little Elsie Breckmann to lead her to death. And how about the paranoia induced by the dancing shadows during that aforementioned pursuit scene? Hitchcock would make prominent use of this very technique in films like The Man Who Knew Too Much as well (a film that also starred Peter Lorre).
Lang also influenced the American film noir genre. Lang would make film noir of his own, most notably with The Maltese Falcon, but there is no doubt that so much of the genre is indebted to M, with that similar sumptuous play of light and shadow and the keen sense of using just the right editing to build paranoia, tension, and suspense.
