To be a Muslim you must sincerely believe in the absolute oneness or uniqueness of God, this is an Islamic concept known as Tawhid. A true believer sees Allah as the only entity worthy of worship, there's no other, no partnership, nor idols that is deserving of praise.

Allah is the ultimate creator, there's no close second. It is only through his will that things happen.

The other condition of being a Muslim is the belief in Allah's last and best messenger, Prophet Muhammad (sallallahu alaihi wasallam).