Many have tried to explain the Triune God in simple language using various analogies. My favorite is water. Liquid water is H2O. Ice is H2O. Water vapor is H2O, Water, ice, and vapor are different forms of the same substance.
Father, Son, and Holy Spirit are of the same substance as stated in the Nicene Creed. Here is a sample of the many scriptures that support the Trinity.
Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: (Matthew 28: 19 KJV)..
At that time Jesus came from Nazareth in Galilee and was baptized by John in the Jordan. As Jesus was coming up out of the water, he saw heaven being torn open and the Spirit descending on him like a dove. And a voice came from heaven: “You are my Son, whom I love; with you I am well pleased” (Mark 1: 9-11 NIV).
In the beginning was the Word and the Word was with God and the Word was God. All things were made by him; and without him was not any thing made that was made (John 1: 1-3 KJV)
And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth (John 1: 14 KJV).
He [Jesus] is the image of the invisible God, the first-born of all creation. For by Him all things were created, both in the heavens and on earth, visible and invisible, whether thrones or dominions or rulers or authorities–all things have been created by Him and for Him (Colossians 1: 15, 16 NASB).
“Philip said to him, Lord, show us the Father, and it is enough for us.” Jesus said to him, “Have I been so long with you, and yet you have not come to know Me, Philip? He who has seen Me has seen the Father; how do you say show us the Father?” (John 14: 9 NASB).
And God said unto Moses, I AM THAT I AM: and he said, Thus shalt thou say unto the children of Israel, I AM hath sent me unto you (Exodus 3: 14 KJV).
Jesus said unto them, Verily, verily, I say unto you, Before Abraham was, I am (John 8: 58 KJV)
The LORD said unto my Lord, Sit thou at my right hand, until I make thine enemies thy footstool (Psalm 110: 1 KJV)
While the Pharisees were gathered together, Jesus asked them, Saying, What think ye of Christ? whose son is he? They say unto him, The son of David. He saith unto them, How then doth David in spirit call him Lord, saying, The LORD said unto my Lord, Sit thou on my right hand, till I make thine enemies thy footstool? If David then call him Lord, how is he his son? (Matthew 22: 41-45 KJV).
I will declare the decree: the LORD hath said unto me, Thou art my Son; this day have I begotten thee (Psalm 2: 7 KJV).
God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets, Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds; Who being the brightness of his glory, and the express image of his person, and upholding all things by the word of his power when he had by himself purged our sins, sat down on the right hand of the Majesty on high; Being made so much better than the angels, as he hath by inheritance obtained a more excellent name than they, For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son? (Hebrews 1: 1-5 KJV).
For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace (Isaiah 9: 6 KJV)
To wit, that God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them; and hath committed unto us the word of reconciliation (II Corinthians 5: 19 KJV).
The doors were locked, but Jesus came and stood among them and said, “Peace be with you.” Then he said to Thomas, “Put your finger here, and look at my hands; then reach out your hand and put it in my side. Stop your doubling, and believe!” Thomas answered him, “My Lord and my God!” (John 20: 26b, 27 GNT).
Again the High Priest questioned him, “Are you the Messiah, the Son of the Blessed God:” “I am,” answered Jesus, “and you will all see the Son of Man seated at the right side of the Almighty and coming with the clouds of heaven!” (Mark 14: 61b-62 GNT).
But Stephen, full of the Holy Spirit, looked up to heaven and saw God’s glory and Jesus standing at the right side of God (Acts 7: 55 GNT).
We have not depended on made-up stories in making known to you the mighty coming of our Lord Jesus Christ. With our own eyes we saw his greatness. We were there when he was given honor and glory by God the Father, when the voice came to him from the Supreme Glory, saying, “This is my own dear Son, with whom I am pleased!” We ourselves heard this voice coming from heaven, when we were with him on the holy mountain (2 Peter 1: 16-18 GNT). See Luke 9: 28-36 also.
Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come (John 16: 13 KJV).
For no prophetic message ever came just from the human will, but people were under the control of the Holy Spirit as they spoke the message that came from God (2 Peter 1: 21 GNT).
When the day of Pentecost came, they were all together in one place. Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. They saw what seemed to be tongues of fire that separated and came to rest on each of them. All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them (Acts 2: 1-4 NIV).
Hearken unto me, O Jacob and Israel, my called; I am he; I am the first, I also am the last (Isaiah 48: 12 KJV).
Behold, he cometh with clouds; and every eye shall see him, and they also which pierced him: and all kindreds of the earth shall wail because of him. Even so, Amen. I am the Alpha and the Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty (Revelation 1: 7, 8 KJV).
I was in the Spirit on the Lord’s day, and heard behind me a great voice, as of a trumpet, Saying, I am Alpha and Omega, the first and the last: and, What thou seest, write in a book, and send it unto the seven churches which are in Asia; unto Ephesus, and unto Smyrna, and unto Pergamos, and unto Thyatira, and unto Sardis, and unto Philadelphia, and unto Laodicea. And I turned to see the voice that spake with me. And being turned, I saw seven golden candlesticks; And in the midst of the seven candlesticks one like unto the Son of man, clothed with a garment down to the foot, and girt about the paps with a golden girdle. His head and his hairs were white like wool, as white as snow; and his eyes were as a flame of fire; And his feet like unto fine brass, as if they burned in a furnace; and his voice as the sound of many waters. And he had in his right hand seven stars: and out of his mouth went a sharp two-edged sword: and his countenance was as the sun shineth in his strength. And when I saw him, I fell at his feet as dead. And he laid his right hand upon me, saying unto me, Fear not; I am the first and the last: I am he that liveth, and was dead; and, behold, I am alive for evermore, Amen; and have the keys of hell and of death (Revelation 1: 10-18 KJV).