A sharp observation — and the answer is sitting in the very verse in front of you. "Elohim" (אֱלֹהִים) is indeed a plural form from the family of El and Eloah (אֵל / אֱלוֹהַּ) [S1][S2]. But look at the verb:
Genesis 1:1 בְּרֵאשִׁית בָּרָא אֱלֹהִים אֵת הַשָּׁמַיִם וְאֵת הָאָרֶץ — In the beginning God created the heavens and the earth.בָּרָא ("created") is a singular verb. If Elohim were a true plural, the Torah would have to say בָּרְאוּ — "they created." Throughout the Tanach, when Elohim refers to the God of Israel it takes singular verbs and adjectives; the lexicon accordingly calls it a "plural intensive" with singular meaning [S1]. Ibn Ezra, commenting on this very verse, explains it as the honorific plural natural to Hebrew — a single master is called "adonim" or "be'alim" — "and therefore the verse says bara, and not bar'u."
When the word really is plural, the grammar tells you: "other gods" in Exodus 20:3 takes the plural adjective אֲחֵרִים. The word can even mean human judges: Exodus 22:7 says the owner of the house "shall come before ha-elohim," and Rashi glosses that plainly as coming "before the judges" (אל הדיינין) to stand trial. Elohim is a title of authority and mastery — and its bearer par excellence is the One God, as the Torah states outright:
Deuteronomy 6:4 שְׁמַע יִשְׂרָאֵל יְהֹוָה אֱלֹהֵינוּ יְהֹוָה אֶחָד — Hear, O Israel: Hashem is our God, Hashem is One.A plural of majesty in form — one God in every verb, every adjective, and in the Torah's own declaration.