By default, Ubuntu has a rather boring terminal. It features a solid purple background, no transparency, and white text. To make it look matrix style with green on black text and a transparent window, follow these steps:

Open a terminal window:

Click on Edit > Profile Preferences:

On the Colors tab, uncheck "Use colors from the system theme" and then select Green on Black from the "Built-in Schemes" list:

On the Background tab, select "Transparent Background" and adjust the slider bar to your preferred level of transparency:

You now have a transparent, green on black, matrix style terminal window!