In the song, Maui told Moana about his amazing deeds.  Why - he pulled up the islands from the sea, he lifted the sky, he even found fire and gave it to humans!  As a demi-god, Maui was born with special powers. Demi-god means one parent is a god and the other is human. Maui’s father was the god and his mother was human.
People from the Pacific islands tell many stories about Maui the demi-god.  Their stories about Maui are not quite the same as what you saw in Moana. The way they tell it, Maui may have three or four brothers. Or he may have a sister named Hina.  If someone from those islands told you stories about Maui, they may sound like this:

Maui Pulls Up the Islands
One day Maui said to his four brothers, “Come fishing with me today!  Let’s go far out to sea. The fish are much bigger and better there, than they are close to land.”  
“Okay!” said his brothers.  They were good fishermen and wanted those big fish.  The four brothers and Maui jumped into their canoe and started to row.  When they got far out to sea and could no longer see land, Maui jumped onto the end of the canoe.  He drew out his magical fishing hook. When his brothers were looking ahead, he cast the hook over the side of the canoe.  The hook sunk down deep into the blue water.  

When his brothers were not looking, he cast his hook into the blue waters.

Soon, the magical hook stuck fast to the bottom of the sea. Maui pulled the fishing line tight.  He called out, “See that tug? I must have hooked a giant fish!”
“Wow, I see that!” said one brother. 
"That is some fish you caught!" said another.
“My brothers!” Maui called out.  “Paddle hard so we can bring up this great fish!”
The brothers paddled with all their might.  They paddled so hard they did not see that the hook was pulling up the land from the bottom of the sea.  Behind them, one island after another rose from the sea!
Legend says that is how Maui made the islands, where the people now live.

Maui Catches the Sun
One day, Maui wanted to see how life was for the people who lived on the islands.  But what he saw there made his heart skip a beat. Life was very hard for them. And he could see why - the days were just too short!  There was not time in a day for people to do what they needed to do, like making and cooking food. If they laid out a wet blanket on the sand, the blanket would still be wet the next day.  There was not even time for the fruit in the trees to get ripe.
“It is that Sun!” said Maui.  “He is racing too fast across the sky!  He is not thinking about the people who live down below, on the islands.”  
Maui knew it was up to him, a demi-god, to slow down the Sun. But how?  He asked his brothers. He asked his sister Hina. He asked still others that he knew.  
“Who do you think you are, Maui?” said one.  “No one can catch the Sun!”
“Even if you are a demi-god,” said another, “you know very well the Sun is too big and bright for anyone to stop.”