a literal interpretation
this is my interpretation, i had to stretch a bit with the back story, but it isn't completely out of nowhere:
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daft punk exists in our time. they are two robots who desparately want to be human. their method of going about this is making music that humans will love and respect.
unfortunately their plan backfires. instead of being accepted as human, the humans make themselves more like the robots. daft punk, no longer individuals go into self exile.
at the start of the movie daft punk is told my whatever organization (the US government perhaps?) that they need to make humans stop wearing the masks. daft punk is told they can be made human. after being made human, daft punk's mission will be to seen to as many people as possible as 'human.' therefore making everyone want to take their masks off and be human again. after this is done, daft punk assumes they will blend in as humans. (because in their mind their going to become humans)
this is why a happy song is played in the intro while they're driving. they're excited during the long road trip. they will soon be human.
after a quick drive through a suburban town, (where we see people are still wearing the robot masks) they arrive at the facility where the transformation will take place.
unfortunately, daft punk is not human. they cant take off their robot masks, because they're not masks. the solution to this is to pour latex over their heads, and design giant human-like masks over them.
the result, of course, looks ridiculous, but the hero robots of daft punk are too excited and invested in this, and they believe they have become human.
after the masks are finished, the hero robots are off to walk around town. they make quite a commotion. everyone who sees them stop what they're doing and stare. it seems to them like humans are walking around without masks, but something is wrong.
this is when the summer sun starts hitting them. the heat begins to melt the latex. it is probably magnified by the heat of the metal helmets under them. this riles up the locals. they know they were trying to be tricked. they start to close in on our hero robots.
staggering from the heat, melting latex, and the approaching crowd, daft punk hides out in a nearby bathroom.
it's very emotional for them to see their human faces melting off. hero robot #2 accepts this a little faster, and tears off the melting face. hero robot #1 stares at his humanity melting away, hes taking it harder than #2.
finally #2 is clean from his mask. he gives #1 a few moments, then makes it clear its time to clean himself up, and go back to exile.
after a few minutes they emerge from the bathroom as daft punk, and start to make the vast trek home by foot.
the trip is long, and it gives robot #1 plenty of time to think about the fact that he is not human. this was his big chance, but all it did was make him realize his dream will never become true. he is not human, and he will never be human.
he staggers behind a few times on the trek until he is finally overcome with his feelings of inadequacy. he lets robot #2 know he doesnt want to go on. its time for robot #2 to do him a favor and activate his self destruct sequence.
after robot #1's suicide (or 'deactivation') robot #2's trip becomes harder. eventually the agony and now isolation gets to him. He gives up and tries to initiate his own self destruct sequence. Unfotunately, he cant reach his own. and hes all alone.
in agony he takes off his helmet, revealing how unhuman he really is. in frustration he stares at his helmet in disgust, and ultimately smashes it on the ground.
while picking up the pieces he notices the visor is magnifing the sun. by holding it to his hand it catches his closes on fire. as we see his glove melting away we can see his hand is also robotic.
the last scene is him walking away while he burns off the last shread of humanity, his fake body.
(in a sequel we could see where he was going, or what he looks like as a complete robot...heh.)