Regarding 'Metropolis' and its introduction of the robot/android trope to sci fi, I'm actually pretty interested in how the concept,as it's presented, diverged and melded into the modern day's more common associations regarding the presentation and expectation of robots.  Nowadays, robots and their behavior are treated in a varying amount of ways, and are all labeled differently according to the different factions that have adopted and changed the concept to better fit their works.  Be them synths or AI, reliant on programming alone or self-teaching, there are many ways to pull off the ever-expanding robot motif. 

In 'Metropolis,' it's clear that the robot wasn't regarded in a moral light.  It's purpose was to incite conflict, and upon it's brutal, but well deserved destruction, when its identity was revealed, no one regarded the being as a someone, and it's 'death' was deemed hollow in the minds of the masses.  It was evidently sapient enough to follow through with orders, as well as to know how to manipulate people emotionally, but above all else, it was aware enough to become more sadistic and malevolent than it was intended to be, and as a result, it caused more damage than it was supposed to.  While not exactly a positive development, it was a glimpse, though likely unintentional, into the being's ability to grow beyond a dictated purpose and programmed persona, as well as commit acts it wasn't specifically told to do.  This potential sparks a large amount of questions as to whether or not the being could have sook and pursued other things of it's own volition while existing. 

The intense and seemingly insane demeanor is a reoccurring theme amongst the robot trope, often meant to illustrate a robot's inability to function in the place of a human due to some underlying instability that would certainly come to surface once having interacted with and having prolonged exposure to the real world.  It's usually meant to do the opposite of what I've been implying, which is humanizing them.  We fail to see them as possible individuals as cognitively and psychologically capable as ourselves, which is why any and all of their actions tend to just denote them as props to aid or inhibit progress.  The robot Maria was used to start a class uprising that would easily justify the use of force to oppress the masses, but went on to do so much more morally reprehensible things, like nearly kill all the children of a particular people, and severely damage the system by which the city mechanically functions, with no visible reason why.  This type of horrifying behavior is after attributed to the sub trope of an amoral robotic character who acts in a manner that disregards emotions and engages in behavior that is considered close minded, logically steeled, and cold.  It's the type of thing meant to strip a robot of any trace of a relatable, human aspect, as an excuse to have someone who it is justifiably disliked for the literally senseless antagonism they achieve.  Tons of movies do it, where the robotic characters do things inhumane, but instead of solidifying their actions as that of a villain, they're sorted into the whole 'programming without moral regards' thing, which takes away the notion that perhaps they're just capable of being bad people in favor of passively misused objects.  I actually enjoy seeing old perceptions of robots and comparing them to the more modern incarnations we have today due to the fact that it shows how much though and real world sense creators of today put into their work, asking the question "should this sapient race of being's so unlike us be considered people?" or even outright saying that yes, they should (which is something that I agree with).

If there were any more for me to say, it would be that I genuinely appreciate Metropolis' addition to sci fi.  The concept of the 'robotic man' is significant, and a foundation for multiple more elements of science fiction.  There's certainly a dichotomy between the visions of robots then and robots now, but I think the trope has taken a turn for better over the decades, personally.  Then again, I have so few examples of fiction I can personally reference, only about half a dozen GOOD sources, so what do I know.

Grain of salt, everyone.