First off, theres several styles that are atleast related to the "Robot." A few of these styles are popping, locking, hitting, and ticking. THERE IS NO SUCH THING AS "Pop n Lock." They are 2 different styles. Probably the closest related to the robot is hitting, and ticking.
To learn Hitting issolate muscle groups, kind of like when you make a fist and flex your bicep. Put out your arm in this position and without making any type of fist, flex the bicep. Do this to the beat of music always hitting the snare. This is the basis of this style. Eventualy you will be able to isolate entire muscle groups and make your entire body tense to the beat. If your going for true hitting however, you will need to really HIT the beat; by this I mean you need to really emphisise it. When the snare hits tense hard and make it look heavy.
Ticking, is another style closely related to this. Ticking has been refered to as "Strobing" which is inncorrect so dont repeat it, however this name does illustrate how Ticking is supposed to look. Ticking is basicly the same as hitting but instead of just hitting the beat with a tensing of the muscles you hit rapidly. If done correctly you the audience will experience an image of you as if you were in a slow pased strobe light. Having the right music can help with this style too.
Get more info on these styles and more here:
http://www.bboy.org/forums/