The Bible teaches there is only one God.

“You are My witnesses,” declares the LORD, “And My servant whom I have chosen, so that you may know and believe Me and understand that I am He. Before Me there was no God formed, and there will be none after Me (Isa 43:10; cf. Deut 6:4; Isa 42:8; 44:6-8; 45:5-7, 21-22; Rom 3:30; 1 Cor 8:6; 1 Tim 2:5; Jas 2:19).

God has always existed eternally as God.  

Before the mountains were born or You gave birth to the earth and the world, even from everlasting to everlasting, You are God (Ps 90:2; cf. Ps 41:13).

God created everything that has been created.

All things came into being through Him, and apart from Him nothing came into being that has come into being (John 1:3; cf. Gen 1:1; Ex 20:8-11; Ps 24:1; Isa 44:24; Col 1:16-17).

God is omnipotent (all-powerful), omniscient (all-knowing), and omnipresent (everywhere present at the same time). 

“Can a man hide himself in hiding places So I do not see him?” declares the LORD. “Do I not fill the heavens and the earth?” declares the LORD (Jer 23:24; cf. Ps 139:7-10; 147:5; 1 John 3:20; Rev 19:6).

God is Spirit, from everlasting to everlasting the same. 

“But an hour is coming, and now is, when the true worshipers will worship the Father in spirit and truth; for such people the Father seeks to be His worshipers. “God is spirit, and those who worship Him must worship in spirit and truth” (John 4:24; cf. Mal 3:6; Luke 24:39; Jas 1:17). 

The Bible teaches that the Father is God.

To all who are beloved of God in Rome, called as saints: Grace to you and peace from God our Father and the Lord Jesus Christ (Rom 1:7).

The Son is God. 

Thomas answered and said to [Jesus], “My Lord and my God!” (John 20:28; cf. Isa 9:6; 40:3; John 1:1-4; 20:25-29; Rom 9:5; Col 2:9; Heb 1:3, 8, 10).

And the Holy Spirit is God.

But Peter said, “Ananias, why has Satan filled your heart to lie to the Holy Spirit and to keep back some of the price of the land? While it remained unsold, did it not remain your own? And after it was sold, was it not under your control? Why is it that you have conceived this deed in your heart? You have not lied to men but to God” (Acts 5:3-4; cf. Ps 139:7-8; John 3:5-7; 1 Cor 2:10-11).

He is one Triune God, eternally existing in three persons—co-eternal in being, co-identical in nature, co-equal in power and glory, and having the same attributes and perfections.

“Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit (Matt 28:19; cf. 1 Cor 12:4-6; 2 Cor 13:14; Eph 4:4-6; 1 Pet 1:2; Jude 20-21).