Here's something I took from another website that can help explain the question.
Isaiah 44:6 reads:
Thus saith the LORD the King of Israel, and his redeemer the LORD of hosts; I am the first, and I am the last; and beside me there is no God.
Passages such as Isa 44:6,8 and 45:5,21 that read "no God beside me" or a variation of that phrase are traditionally interpreted by mainstream anti-Mormons as meaning that other than Yahweh no form of deity exists at all, including exalted men. This type of interpretation at first seems obvious, but after considering similar passages in other parts of scripture it is clear that this interpretation is incorrect.
For example, Isaiah 47:8-10 depicts the city of Babylon as saying:
Therefore hear now this, thou that art given to pleasures, that dwellest carelessly, that sayest in thine heart, I am, and none else beside me; I shall not sit as a widow, neither shall I know the loss of children:
For thou hast trusted in thy wickedness: thou hast said, None seeth me. Thy wisdom and thy knowledge, it hath perverted thee; and thou hast said in thine heart, I am, and none else beside me.
These passages use the exact same phrase as Isa 44 and 45, yet they certainly do not exclude the existence of any city other than Babylon. The city of Ninevah would be very upset if this were the case, as Zephaniah depicts Ninevah in Zephaniah 2:15 as saying:
This is the rejoicing city that dwelt carelessly, that said in her heart, I am, and there is none beside me: how is she become a desolation, a place for beasts to lie down in! every one that passeth by her shall hiss, and wag his hand.
Again it is clear that this phrase does not exclude the very existence of other cities. Using these parallel phrases makes it clear that Isaiah is not excluding the very existence of any other deity when he quotes Yahweh as declaring "there is no God beside me." There are, in fact, several scriptures in the Old Testament that imply that Yahweh is in fact one of a number of Gods, albeit supreme. Compare the following passages from the KJV, NIV and ESV versions of the Bible:
And the heavens shall praise thy wonders, O Lord: thy faithfulness also in the congregation of the saints. For who in the heaven can be compared unto the Lord? who among the sons of the mighty can be likened unto the Lord? God is greatly to be feared in the assembly of the saints, and to be had in reverence of all them that are about him. O Lord God of hosts, who is a strong Lord like unto thee? aor to thy faithfulness round about thee? (KJV Psalms 89:5-8)
The heavens praise your wonders, O LORD, your faithfulness too, in the assembly of the holy ones. For who in the skies above can compare with the LORD? Who is like the LORD among the heavenly beings [fn. Lit "sons of god(s)]? In the council of holy ones God is greatly feared; he is more awesome than all who surround him. O LORD God almighty, who is like you? You are mighty, O LORD, and your faithfulness surrounds you (NIV Psalms 89:5-8).
Among all the gods there is none like unto thee, O Lord; neither are there any works like unto thy works (Psalms 86:8).
God has taken his place in the divine council; in the midst of the gods he holds judgment (ESV Psalms 82:1)
God standeth in the congregation of the mighty; he judgeth among the gods. (KJV Psalms 82:1)
These scriptures speak of divine beings, "gods" who are the "sons of god(s)" who are heavenly beings who dwell in the skies. These cannot be idols or false gods. Yahweh dwells among them, reigns over them, and holds judgment in their midst.
Hope that helps!