Phone is locked need to unlock it droid maxx

I have a droid maxx it did not have a code on it but for some reason now it does have a lock screen,I want to put my SIM card in it and swap over from my galaxy it want let me ? I did the power up and power down button why when I try to power it up it shows a robot man laying down ? And why does this question deal keep saying I need to add more to it

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