We need to be careful of terminology here-- "Alien" in the Bible refers to "foreigner," if I'm not mistaken, which is a term used to describe individuals who are in a country illegally, such as in America, where President Donald Trump is taking actions to deport "criminal aliens," which refers to people living in America without prior authorization from the government.
It is very important to keep in mind that "Angels," are not "aliens." Angels are authorized by God to do His work as messengers and countless other ways. A demon could be called an "alien," since they are NOT authorized to take any actions regarding this world that would interfere with God's will.
But, it is possible that God could use other beings to carry out His work and will, but, this is not a primary concern of human beings, since this has not been revealed through the Bible and salvation history. What is clear--crystal-- is that God is not an "alien," under any definition of this world. "Alien," would describe those who OPPOSE God's will.
God has been revealed to humanity through the Judeo-Christian salvation history of the Bible: Old Testament and New Testament. Beginning with the revelation to Moses, God, or "ELOHIM," "JEHOVAH," "ADONAI," has been revealed as a Father-figure, especially through Jesus of Nazareth. But, the Divine Creator has also revealed Divine Power and authority through the parental model of Father and Mother, and through the family model. I've heard many pastors teach that God is about a personal relationship with His people. He also gave us a lady role-model in the presence of Mary, and many other women in the Bible. And the model of marriage, such as Abraham and Sarah, and the family model of a foster father in the person of Joseph, foster father of Jesus. Also, adoption is blessed by God since Moses was adopted, and Jesus was adopted by Joseph, His foster father. And, Christians are all "adopted," into the family of faith.
But, Even though God is a supreme-being as revealed in many ways in the Bible, He is not an alien being. Someone who has devoted thousands of years to human history, committed to our salvation to the point of even becoming one of us in the Person of Jesus Christ, and preparing the world for this through Judaic history and the ancient scriptures of the Bible--Psalms and Prophets--for over 2,000 years.
God became one of us-- as the Apostle John said: "The Word became flesh." (John 1) or "The Word became a human-being." Jesus is a human being; He is not an alien-being. Even though He is the Divine Son of God, He is still a human being--not a foreigner.
"Foreigners," or "aliens," are those who take actions that are not authorized by God. This would include fallen angels, or "demons," and could include other fallen beings, if there are any that exist who do God's will. If there are so-called "alien-beings," like everything else in Creation, there are likely those who do God's will, and those who oppose Him.
The Bible does describe possible instances of beings or angels or angelic beings, that do God's will. In all cases, God is not a foreigner to this world. He revealed Himself in many amazing ways-- speaking directly to people, which is recorded in the Bible. He is revealed as a very powerful Being of Light, Love, Truth, and Divine Power, Who has created the world for people to live in peace. In most cases in the Bible, His Presence was veiled because of His power to protect us people from being too overwhelmed. He is a God who can easily part the Red Sea, and bury His enemies beneath it if necessary, and then walk over them on the water, as Jesus did, to reveal His power and victory over the enemies of God.
Sometimes the Bible does describe instances where the Divine Presence "ascended with trumpets," angels, music, and other indirect descriptions. If God chooses to travel with some sort of "vessel," it is described as possibly colorful, with music, trumpets, and other ways. IF He is mysterious, it is for a higher purpose.
Most, if not all, of so-called "alien," sightings, tend to be revealed in ways that might appear "eerie," or "cold," or strange, etc... This does not describe the God of Israel. In fact, those kind of vessels that look like "stones," are described as existing in a low valley, and people who are controlled by them do not worship God. Maybe someone could find the verse I'm talking about, since I'm out of time at this computer, or I'll post it later.
The eerie, cold, distant, weird vessels seen in sci-fi, or that might appear in real life, like the bizarre scene I witnessed briefly in a sci-fi movie where a strange humanoid was being forced by a cold, dark saucer, to eat poison and commit suicide in some kind of weird alien sacrifice, do not reflect the God of Israel. His presence is described in the Bible as more like the movie: "Close Encounters of the Third Kind," or colorful, trumpets, music, angels, rejoicing, and a loving being of Light devoted forever to the well-being and salvation of the people of the earth-- the Children of God, as John described.
God is not a supreme-being who is "eerie," or "silent," or "creepy," or strange; He is a supreme-being who loves humanity very much, and even became one of us, to teach us personally, as Jesus Christ. The teachings of the Bible are clear that God cares for His people, and has gone to great lengths to convince humanity that our lives matter very much, and that His rules for life, are established for the benefit of humanity. In every case, when these rules are not honored, bad things always happen. Stewardship matters; Obeying God's rules matters very much.
It's not that difficult to love God, love each other and love God's presence in ourselves in a humble way;
To "worship the Lord," as I heard the voice of one beautiful loving angel, who I perceived as a lady angel, say in a dream sometime last year--
in a loving, but, slightly pleading tone of voice.
The LORD will appear in the sky, "in the same way as He left," as the Angels described when Jesus ascended to Heaven, and also as it was revealed to me in a dream many years ago. He will be Jesus-- and all humanity will know; Not strange flying saucers. So, don't worry about it. God is one of us. Just make sure we are one with Him, and we don't have to worry about anything else that happens in this world.