I actually didn't like the look of the aliens. They looked like humans with a spiky beard and slightly different hands. Battleship suffers from the "Avatar Syndrome" in this respect. There's a big budget and beautiful special effects, God forbid they come up with some creative aliens!
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But I did like how sunlight was too bright for them. Many criticized it for being a lazy plot device, but it's actually wouldn't be too far from the truth. The hints given in the movie make it clear that the aliens are from the exoplanet Gliese 581g. (The discovery date and the distance are inaccurate but that's another rant) The star, Gliese 581, is a red dwarf, which is smaller and significantly dimmer than our own Sun. Any life that originates on a planet around a red dwarf would certainly be accustomed and adapted to the low-light conditions, and the sunlight on Earth would be too bright for them. I thought it was a nice little nugget they put in.