To give your material a more metal-like look you can use the metalness value. You can also use a map for this. The reflectivity of a material can be changed with the roughness value. The lower the value the more reflective the surface will be. The roughness can also use a map.
The clear coat value adds, as the name suggests, a clear coat on the outside of the material. You can use this for things like car paint or materials like carbon fibre. The coat roughness defines the glossiness of the coat.
Fresnel is the term used to describe how the light you see reflects at different intensities based off of the angle you are viewing it from. For example, if you are standing over a pool looking straight down at the pool, you will not see a lot of reflections in the water. As you start to move your head so that the water in the pool becomes more and more parallel to your eye level, you will begin to notice more and more reflections in the water.
If you want to use a colour for fresnel you need to activate Diffuse. In the Diffuse L Color select the colour you want. Use the diffuse parameters to change the fresnel effect.
Use the reflection option to use a fresnel effect on the reflectivity of the material. Use the diffuse parameters to change the fresnel effect.