We use may to refer to weak possibility in the present and future:
The economy may go up or down in the next year. (I think both are possible, the economy going up or the economy going down. I am not making either one a strong possibility.)
I think I may go to the doctor today and try to get some antibiotics. (I am not very sure yet if I will go to the doctor.)
We use may in formal writing, especially academic English, to describe things which the speaker thinks are generally true or possible. In this case, it is a more formal equivalent of can.
A typical farmer’s cottage can be seen in the Ulster Folk Museum.
Both sentences express what the speaker believes to be a general truth about where the cottage is located. The speaker knows that there is a cottage in the museum and a visitor is able to see them there if they want to. May is more formal.
A typical farmer’s cottage may be seen in the Ulster Folk Museum.