To make the modeling as realistic in 3d max, you need mental ray.
Mental ray is used for providing light to the object for the sake of its wonderful appearance. If you have created a model successfully but still it is with out any light dropping, then it needs to catch a light for better and realistic look.
The mental ray provides you light effect for the object. You can easily apply light affect to any material object but it is very difficult to assign light to any transparent material because the light can not pass through from them.e.g. Water and glass in modeling. You can apply light affect over that particular material by using caustic in mental ray.
As you know mental ray is the way to apply light but what is caustic? Caustic is a package of light that reflect or refract from one object to another and assign them light. The caustic focus the materials with strong light at specific position. While applying shadow, you have required assigning spot light using ray traced shade.
Don’t forget to adjust the setting of mental ray at using time. When the light assigning process is completed, then hand over to material. Make sure that you have adjusted the setting of illumination and light in the render set up, and that’s it. Here you project is ready for final rendering. Render the image, it will take much time anyhow the result will be excellent.