The Trinity VS Modalism

Chatting some more to my friend reminded my that there are many different ideas about what the Trinity is, only one of which can be right.

Modalism is probably one of the most common false-Trinities that I have come across people believing, and is the one that my everyone my friend knows think the Trinity is.

Both of us rightly disagree with Modalism. So before I explain why Modalism doesn't work, I should explain what it is.

Modalism is the belief in one God (good!) that has three persons (good!), but these three different persons never exist at the same time, they are just different forms that the one God can choose to take (bad).

In this instance, my friend's point about Acts 7 becomes very helpful:
Acts 7:55-56, "⁵⁵ But Stephen, full of the Holy Spirit, looked up to heaven and saw the glory of God, and Jesus standing at the right hand of God. ⁵⁶ “Look,” he said, “I see heaven open and the Son of Man standing at the right hand of God.”"

Here we've got all three persons of God, in different places, at the same time. This doesn't fit with Modalism.

Going to Matthew 3 we see another clear example, with the baptism of Jesus:
Matthew 3:16-17, "¹⁶ As soon as Jesus was baptised, he went up out of the water. At that moment heaven was opened, and he saw the Spirit of God descending like a dove and alighting on him. ¹⁷ And a voice from heaven said, “This is my Son, whom I love; with him I am well pleased.”"

The "Modal Trinity" isn't suggested by the Bible. The Trinity suggested by the Bible is one God, made of three persons, who eternally exist at the same time. 

(Why do I believe this? Loads of reasons, I listed some in the previous post, here's another:
John 10:30-33, "³⁰ I and the Father are one.”
³¹ Again his Jewish opponents picked up stones to stone him, ³² but Jesus said to them, “I have shown you many good works from the Father. For which of these do you stone me?”
³³ “We are not stoning you for any good work,” they replied, “but for blasphemy, because you, a mere man, claim to be God.”")