how can models help in science, why they are important, what and some examples of models.

Since this is not my area of expertise, I searched Google under the key words "models in science" to get these possible sources:

https://www.google.com/search?client=safari&rls=en&q=%22models+in+science%22&ie=UTF-8&oe=UTF-8&gws_rd=ssl

In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.