The word )LHYM is a generic count-noun, and its reference must be
construed from the context. In addition to Peter's references (and
fine discussion) I would like to point out that the writer of Hebrews
(2:7) in the NT quoted Psalm 8:6 and applied it to the angels. In
some Qumran writings )LHYM refers to the angels as well.
The reference of angels as "gods" in the Tanakh neither indicate
polytheism nor henotheism, because they are not in line of worship.
The angels are said to be sons of YHWH, and therefore they have the
same nature as their father. In a world with different kinds of
Christian dogma it can seem strange that creatures can be referred to
as "gods" beside The God, but evidently this was not strange to the
Hebrew mind.