Dear Mr Smith,
I'm writing to invite you to a lecture held by student union.
It has become apparent to us that some of us can not do well in English, not only in exams, but also in daily life. The lecture will focus on an English party, in order to let students develop interests in English and study English better. Then, there are music lovers singing English songs to make the atmosphere alive. To be sure, there may be difficulties we cannot overcome, but if we work hard, we can figure out another way to solve the problem.
Would you like to come and join us?
We will be very glad if you can come. Only when you come and join us can we achieve complete success. Students from student union will wait for you at the school gate. It will be very cold at night.