In linguistics, grammatical mood is a grammatical (and specifically, morphological) feature of verbs, used to signal modality. That is, it is the use of verbal inflections that allow speakers to express their attitude toward what they are saying (for example, whether it is intended as a statement of fact, of desire, of command, etc.). Less commonly, the term is used more broadly to allow for the syntactic expression of modality that is, the use of non-inflectional phrases. Mood is distinct from grammatical tense or grammatical aspect, although the same word patterns are used to express more than one of these meanings at the same time in many languages, including English and most other modern Indo-European languages. Some examples of moods are conditional, imperative, indicative, injunctive, optative, potential, and subjunctive. Infinitive is a category apart from all these finite forms, and so are gerunds and participles.
For worksheets on mood you have come to the right place. There are now 43 mood related worksheets that can help you when planning lessons on this topic. One mood students will learn about early on is the imperative. Here is a nice worksheet on this mood that focuses on classroom instructions. The first page is great as an introduction or study guide while the other two pages contain excellent practice activities. If your students have already mastered this, consider using a different worksheet instead. Some worksheets will be more suitable for your students than others.
Some moods are simpler and easier to understand which is why all moods are not introduced at the same point in a students study of English. Even beginners will be able to grasp the meaning behind imperative sentences and this is usually introduced when talking about classroom English. The subjunctive mood, on the other hand, is more challenging and even native English speakers often make mistakes. The common structure If I were you ~ sounds correct to native speakers even though they are likely to say things such as If I was a cat ~ which is definitely incorrect. With this in mind, carefully consider whether or not your students are sufficiently prepared before introducing a particular mood.