Monsters

This is not for you if you're expecting an Independence Day-style special effects extravaganza. For a start Monsters was made on a fraction of the budget of the average Hollywood blockbuster - though it makes that into a huge virtue. Rather than a cast of thousands who end up mere cannon fodder, this is basically a two-hander, and a road movie of sorts that is actually a love story at heart, set within a sci-fi framework. The emphasis is on character rather than spectacle, as cynical journalist reluctantly leads the boss's daughter to safety through the Infected Zone of Mexico. Expectations are subverted: it's the poor little rich girl who can speak Spanish (Andrew relies on her translating skills) and who empathises with the locals (the elusive prize for the journalist is a photo of a dead child) Their backstories get gradually sketched in and the development of the relationship doesn't feel forced.
In a similar manner, that title isn't all that it seems. Your interpretation of it changes over the course of the film. The creatures (never "monsters") can be incredibly destructive and chillingly deadly (see the night vision opening and the aftermath of the forest encounter) but as one of the locals comments, if you don't bother them, they don't bother you. Difficult to believe when the landscape is littered with the evidence of their power (vehicles of all kinds and sizes thrown into trees or dumped into the water) and yet proved to be completely accurate when Sam and Andrew watch entranced as two huge bioluminescent creatures entwine in a strangely beautiful mating ritual (the same description could be used to describe the glowing egg sacs on the trees) The creatures pay no heed to the two humans and leave without causing any damage to the truck stop. This isn't an invasion, it's the result of an accident - courtesy of NASA - but like in District 9, the two species can't peacefully co-exist, at least in the minds of the humans. Or to be more accurate, in the minds of the military and those north of the border. The local populace simply carry on with their daily lives, knowing the creatures' annual mating season requires extra caution. The Americans in contrast launch bombing raids on the Infected Zone and build a huge wall at the border - and just like District 9, you don't have to dig too far for allegorical readings. Yet the military are clearly fighting a losing battle, and the wall simply can't keep out the creatures. It's a war that can't be won although the Americans don't seem to have realized that yet. You suspect they never will.