The functional-systemic grammar is particularly concerned with the role of mood in performing interpersonal meta-functions. The mood is an indispensable and universal category for most languages, expressing the speaker's attitude and communication behavior towards the utterance content and the listener. In English, it is a grammatical category associated with a clause with the finite verbs and together with a tense that is considered a marker to distinguish between the invariant and unmodified types of verbs. Metaphors of mood are represented by one or more grammatically specific variations in terms of mood. This mode at the level of compatible expressions can be transformed into metaphorical expressions, making the language's ability to choose extremely rich and adaptable to speech situations. The article will (1) generalize the content of the metaphor of mood, analyze and make statistics of the metaphor of mood in four subgroups: declarative, interrogative, imperative, exclamatory, and the transformation of mood from congruence expression to metaphorical expression; (2) relate to Vietnamese - a language that is different in terms of typology from English, but it has similarities in the way it reflects the speaker's behavior, nuances, and intentions; (3) make use of auxiliary verbs (English) with particles denoting mood (Vietnamese) when expressing mood in metaphorical expression; (4) suggest some ways of applying the grammatical metaphor of mood to increase the effectiveness of communication.

KEYWORDS: Mood; residue; subject; finite; mood particles