Holy angels have not sinned and are not in need of redemption so they would not call God, “Father.” The wicked fallen angels cannot be redeemed and would never call God, “Father.” Although these fallen angels may call Lucifer (the devil who is Satan), father, as some out spoken Satan worshipers do. God is the Creator of all created beings so the holy angels perhaps might think of God as Father but generally God as the Father is in reference to those (mankind) who have been redeemed by salvation in Christ as written in the Holy Bible.