You are in grade five, so am I. You should write an explanatory essay for this composition. Anything can be introduced, such as household appliances, that is, microwave ovens. You can think of a very different introduction at the beginning, just like the class of "New Glass", and use a short story to arouse the items you want to introduce. Then you can make a detailed record. You can find some information about microwave ovens online and in books, and record it digitally, such as how much voltage and frequency it has. In this way, this paragraph is over.

Then you can give some examples about the principle of microwave oven, such as what is the structure of microwave oven and what functions it has, and then this paragraph is over.

In the next few paragraphs, you can use all the explanations. Of course, you can't use comparison, because comparison is to compare with the old style when introducing new items, but you are introducing things, not new items.

Of course, you don't have to write in the microwave, but you can use these writing methods. Open mind and feel free. You can choose anything to write. And I hope what I said is helpful to you. Thank you!