If you use one of the common TeX-Distributions like TeXLive or MiKTeX then you already have a couple of ready made fonts on your computer. You don’t have to use the MetaFont program yourself to create any fonts. Of course you can learn how to use MetaFont and how to design fonts but this is more art than science and requires lots of experience to arrive at usable results.
When you use one of the TeX-Distributions mentioned above to create a document, the default font used “out of the box” will most likely be the font named “Computer Modern” (CM) or perhaps its newer incarnation named “Latin Modern” (LM). These fonts were created using MetaFont. So you dont’t have to do anything special to use a font that was made with the MetaFont program.
As fonts are a piece of art some fonts are perceived different than others. There are many fonts out there and which one’s are considered as “looking good” depends very much on one’s taste and what one is accustomed to. I would say that “looking good” is only a secondary target when choosing the right font for a project. Selecting a different font within LaTeX typically requires the use of a package that performs the necessary configurations.
Regarding your last question: The input to the MetaFont program is a mathematical description (not necessarily vectors as in linear algebra) of a collection of strokes that humans perceive as letters, numbers and other symbols when they see them printed. As such they do not suffer from scaling. However depending on the (mis)configuration of your TeX-distribution rasterization may occur early. Then bitmaps of the letters, numbers and other symbols are created that look jaggy when they are magnified.
Scaling fonts is however not a very good idea, as they are usually designed to “look good” at a certain size. That is why fonts usually offer only a limited number of different font sizes. The “vector format” or better the “size independent description” is not meant to allow scaling, rather it allows the rasterization, which ultimately happens every time before text is printed or displayed on screen, to use different resolutions. Thereby creating the illusion of a smooth stroke.
MetaFont is not the only tool to produce fonts in a size independant format. Other tools can do that too. So only looking for fonts created with “MetaFont” is misleading. Apple’s TrueType fonts, Adobe’s Type 1 fonts and OpenType fonts all have this property of a size independant description without MetaFont being involved in the creation of fonts in those formats.