It is most likely if real "aliens" came, they would be wearing some sort on suit on to be protected from earth. If the alien was an organic life form, being exposed would be bad because:
1-Bacteria and germs in the air (we are used to) would harm them because their immune system isn't used to it.
2-Most likely, their "home-world" would contain a different type of atmosphere unlike our own, so breathing in the nitrogen-rich atmosphere could kill them.
If you mean if the alien was in a suit and it touched you: 1 recomendment~
Wear gloves and and have some portable sanityzer handy (or a sink with a bar of soap)
It would depend on the type but Predetor would probably win.
When an alien species enters into a new environment it has no natural predators. Anything that could eventually become a predator would be standoff-ish at first since the alien represents something new and is thus feared. Once the new predators realize how to kill the alien species their population will deminish and eventually become under control.
Physical Model
Nothing would happen.
In the most bizzare sense, one would have to use a binary method and or pictures to describe with a universal language what the microwave does with either hand pointing and showing of fingers as a system of counting, then show them the demension of the microwave to that particular alien. However depending upon the type of alien, they may have telepathy or even understand what one could be saying through some means of tapping into the other beings mind.
ninjas happen
Then I would get my Green Card
Unexplained Mysteries - 2003 Touched by an Alien was released on: USA: 7 May 2004
there harmless
Nothing would happen as it would just go onto your skin
She'd file a lawsuit.
they might die
It may try to bite.
if you touch it then you will lose touch .
you would get bummed by an alien
you will burn and burn and it will hurt alot
You'd go BOOM! ha ha ha :)