This chapter explores the metaphysics of properties and relations, offering a detailed analysis of competing theories. It begins with a discussion of nominalism about properties, which denies the independent existence of properties, replacing them with linguistic or conceptual constructs. The text contrasts this with realism about universals, arguing that universals ground similarities among objects. Trope theory is introduced as an alternative, positing that properties are non-repeatable entities specific to each instance. The chapter also examines the conception of properties as classes of individuals, assessing its explanatory flexibility. It also discusses problems affecting this conception, such as the difficulty in distinguishing between necessarily coinstantiated properties. Two key distinctions among properties are then drawn: sparse vs. abundant properties (based on their nomological relevance) and intrinsic vs. extrinsic properties (depending on their dependence on entities external to those instantiating them). The final sections explore kinds and types, focusing on their shared and distinct attributes relative to properties, and relations. As regards relations, the following issues are discussed: the real difference between properties and relations; infinite regresses; the distinction between converse relations.