Metadiscourse is writing about your writing. It seems uncessary to write about what you will write about. Here are some examples of metadiscourse:
If the reader wants to read about it twice, she will read the article twice! Use titles or topic sentences to cue your reader to subject matters. If I want to find out what a paragraph will be about, that is where I will look. Perhaps metadiscourse has a purpose somewhere; I generally find it nothing more than an annoyance. Metadiscourse needlessly increases article length and only makes it more difficult to glean useful information.