You are correct--I overestimated your knowledge of literal interpretation. I assumed you knew how we do that. It appears that you have never taken a course on hermeneutics or studied it for yourself, so perhaps I can help you.
The technical term for what I called "literal" is "grammatical historical-interpretation." It involves taking the text for what it directly says in the grammatical sense (according to the syntax and semantics of the original) and its historical sense (understanding the issues of the day in which the work was written). It is literal in the sense that it takes the text directly for what it says, not inserting meaning outside of the syntax and semantics of the original. It is not literal in the sense that it twists figures of speech to interpret them literally, against the nature of such expressions.
The grammatical-historical interpreter interprets figures of speech as just that: figures of speech, not meant to be taken literally. For example, one of those is the metaphor. This is a "Figure of speech in which a word or expression normally used of one kind of object, action, etc. is extended to another" (P. H. Matthews, Oxford Concise Dictionary of Linguistics, p. 243). Those who, like me, take the futurist view of Revelation are well aware that the book is full of metaphors and other figures of speech, and interpret those figures of speech accordingly. So the sword coming from the mouth of Christ is obviously a metaphor for the Word of God, which metaphor had previously been taught in several NT passages.
"In contrast to the other approaches to the book of Revelation, the futuristic position allows a more literal [not "completely literal--JoJ] interpretation of the specific prophecies of the book. Though recognizing the frequent symbolism in various prophecies, the events foreshadowed by these symbols and their interpretation are regarded as being fulfilled in a normal way" (John Walvoord, The Revelation of Jesus Christ, p. 21).
I hope this helps.