I am here all the time,
Even if you can not see me,
I appear to be as big as a dime,
I am able to do something different,
But closer than another galaxy,
I am important in your life,
In more than just a couple ways.
Am I the Sun, a Planet, or the Moon? Answer The Sun!
The clue was the last two lines: The Sun is important in your life because we could not live on Earth without the Sun warming us, helping our plants grow, and helping us see.