Flies is possible to be a noun or a verb. As a noun, it refers to a type of tiny winged insect often attracted to putrid smells and can be often found in dumps, garbage sites etc.
A. (noun) "The arena of warriors has been invaded by a hoard of flies feeding on the remains of the fallen heroes."
As a verb, it stands as a conjugate to the word fly which means to 'move through the air'.
B. (verb) "At the break of every dawn, the bird flies to window to sing a melodious tune."
Flys has no place in contemporary or modern English. It used to be the plural noun used to refer to a unique mode of transport. Its use in modern times is void.