Robot-X was invented to serve humanity and is the first robot able to think for itself. A newspaper editor leads a crusade against the robot, fearing it is the first of a new race that will destroy humanity.
Robot-X, after being persecuted, flees to a factory. It creates an army of intelligent robots and defends itself from humanity.
Robot-X storms the newspaper where the hostile editor works, and reveals him and his cohorts to be "Martians" - based on their appearance, almost certainly Skrulls. The aliens wanted Robot-X destroyed since it would surely have been an essential part of Earth's defences when they invaded.
Robot-X, having saved Earth from the alien fifth column, self-destructed with all his brethren, realising that humanity can't coexist in peace with its superiors, even ones as benevolent as... ROBOT X.
This is the first of a whole series of sequentially named robots with X- serial numbers in Marvel comics. They culminate in X-51, Machine Man.