如何写cover letter

Dear HR Manager,
I would like to apply for the Summer internship Program. As a second-year-postgraduate student major in Mechanical Engineering, I have some basic knowledge on both mechanical engineering and chemical industry.
I have a friend who is one of the interns of your last Summer internship Program. She told me many things about her experiences in your company.And that is why I am really fond of that kind of life: to corporate with excellent workmates, to solve problems in a challenging circumstance and to enjoy thedelightfulness of accomplishing tough tasks. I will really appreciate your kindness if you offer me such an opportunity to join the big family of XXX.
You can contact me any time at your convenience, looking forward to your reply and thank you for your consideration.
Best Regards!

从广义上来说，cover letter是指在正式文件之前的一封简短的说明信。例如你要通过传真发一份文件 在该文件的最前面要附一cover letter，说明你要发的文件等等简短的几句话即可。
它不是仅仅局限在求职信中，它的应用范围很广。不过一般我们说到cover