"We are men."
Translation:Nous sommes des hommes.
It is incorrect. Nouns must always come with their articles. Without articles, you wouldn't know if it were plural, singular, belonging to someone, belonging to a group, etc. because after the noun is changed to plural, in this case homme to hommes, it is still pronounced the same.
Des or les in conversation will tell you that this person is talking about mulitple men.
"Des" is a contraction of "de les" in the same way that "du" is a contraction of "de le". "Du" and "des" literally translate to "of the", but they way I see it, there is an implied "some" in there.
"les hommes" = "the men (that exist)" = "(the) men"
"des hommes" = "(some) of the men (that exist)" = "(some) men"
In this case, the second option is better because we are not talking about an already specified group of men, nor do we mean men in general. It's sort of a new group of men being introduced, much like you'd say "I am a man," in the singular. "A", not "the". The plural of "a" can be considered "some", but more often it's just nothing. In French, it's "des".
Remember, In French you always need an article in there, or else you wouldn't be able to tell singular from plural in speech. So just plain "hommes" is not an option.
"Sommes" is used with "nous" and with "tu" we use "es". I'm pretty sure "sommons" doesn't exist. http://french.about.com/od/verb_conjugations/a/etre.htm