Watch the Week 1: Matching Elements online guitar lesson by David Wallimann from Playing Modal Made Easy
Any musical elements can be classified into the following two main categories: Major or minor.
The 3rd determines where the element goes.
|Major Modes||Minor modes|
Remember that in order to play in key, musical elements need to match. For example, if a chord has a major 3rd, you will need to use a major mode. The more notes a chord has, the less options you will have as far as which mode to use.