Blender has a simple rule regarding materials that you may want to remember, which is that any material must have an object associated. What happens if you don't follow that rule? If Blender finds a material that doesn't have an object, it will purge the material from your file.
What if you want to keep a material with no object assigned? For that, you will find something called Fake User to protect materials from a possible exclusion.
Before we take a look at the Fake User controls, let's see where to set up and configure materials. You will find the controls on the Materials tab in the properties window. Select an object, such as our chair, and open the Materials tab.
You may see an empty panel if your object doesn't have any materials. In this case, you can either click the New button to create an empty material or use the button on the left and pick an existing material from your file, as denoted by the red arrows in the following screenshot:
Once you create a material, you will see more controls to set all visual properties of your surfaces. In the following screenshot, you will see a breakdown of the controls:
What about the Fake User? If you want to protect the material, click on the F button and you will preserve the content.
Notice that you also have a button called Use Nodes. When this button appears, it means you don't have shaders associated with the material. In this case, you should press the button to display advanced shader options.