I can teach grammar or literature. I have lesson plan ideas, but five minutes is tough. It is a mini-lesson for an education class.

DOGDaily Oral Grammar.
Have a handout of 3-5 sentences that cover the same concept like subject-verb agreement (you could put these on an overhead).
Have the students correct the sentences.
I did this with my students. After checking essays, I would pick out errors that I saw most often, and then we would concentrate on those errors. It seemed to help.

Try playing with punctuation, as in, "When you eat your napkin should be in your lap" or "Those old things over there are my husbands." Whenever I pulled these out, my kids begged for more! Do you have a copy of "Eats, Shoots and Leaves"? If not, better get your hands on it!

Try using art as a comparison to literature. Take the way different authors use words in certain arrangements to help the reader use his/her imagination to "paint" a picture. Then compare it to colors artist use. That may work.

Good Luck!

depending on the level you are teaching.. flash cards are really useful... use them creatively to teach nouns advrbs adjectives etc... have a quick hang man sort of a game... or as silly as it sounds try action songs...... i cant help but wonder how you are expected to teach a class in 5 minutes!!!!ooops i missed that you said high school... try having the class weave a story or right a song.. would giving some sort of home assignments help?

A great series of books for mini lessons is Daily Warm-ups (Publisher Walch) they have all different books : one for poetry one for grammar Shakespeare etc...

One of my favorites is the 5 minute poem. Give students an adjective, a noun and a verb and have them write a short poem using at least one poetic element (simile, metaphor etc..)

Another idea that always works is Daily Oral Language..Write sentences on the board and have students correct the grammar and wording.

Try having students work on showing rather than telling in there writing. Explain quickly that telling me your are cold in writing is different than showing me in writing by putting "I was freezing. I could see my breath coming out when I breathed and my hands felt like Popsicles fresh from the freezer." After that have them try to fix one ex: It was hot or I felt sick.

Also, Daily quotations..Pick a quote and have students discuss what it means together. Relate it to other things going on.

Think of activities that are more review that a start of a new lesson..Most of the mini lessons I do are refreshers.
Hope these helped