The course offers an overview of this interesting but complex topic. We will first familiarize ourselves with different types of modalities (alethic, epistemic, and deontic) and then limit our attention to alethic modalities (metaphysical, natural, conceptual, logical, and so forth). How are they connected, and can they be unified? Finally, we will focus on metaphysical modality and its source. We will critically discuss several interpretations representative of various approaches (reductive and non-reductive, realist and anti-realist, and so forth). Interpretations from the second half of the previous century are usually set within the framework of possible worlds, so the fundamental question becomes the nature of possible worlds. Recent interpretations tend to tackle the issue of the source of metaphysical modality directly, and of special importance here is the relationship between metaphysical necessity and essence. Is essence reducible to necessity or is necessity grounded in essence?