"I am a fly."
Translation:Je suis une mouche.
Guessing from your homestuck profile pic you might be interested in this: http://www.stoubs.com/mspa/index.php?aventure=hsfr&page=1 It's HS translated to French!
If I wanted to say "I am a dog" I would say "je suis un chien". If I wanted to say I am a female dog, I would say "je suis une chienne", right? So if I'm saying I'm a fly, can't I say either "une mouche" or "un mouche" Depending on my Gender?
Masculine and feminine are grammatical genders existing in a number of languages.
I am not sure we know how or why some languages have classified or typed nouns in 2 genders (+ neutral, like in German or in Latin), but that is a fact we just have to accept.
I suggest you just learn every new noun with its indefinite determiner, like "un-chien" or "une-mouche", as if they were one-word, so that you assimilate their sound with their gender at the same time, which will ease memorization.