Here is an article "Metaphors in ACT: Understanding how they work, Using them, and Creating your own" discussing the use of metaphors in ACT, from an RFT perspective, as well as from the perspective of the clinician. This article aims to help practitioners understand RFT in basic terms and to see how it applies directly to clinical work through the creation and use of metaphors. Jean-Louis Monestès and Matthieu Villatte authored the article, and interviewed Yvonne Barnes-Holmes (both a clinician and RFT researcher).

You can also read two books:

• Metaphor in Practice: A Professional's Guide to Using the Science of Language in Psychotherapy by Niklas Törneke M.D.
• The Big Book of ACT Metaphors: A Practitioner's Guide to Experiential Exercises and Metaphors in Acceptance and Commitment Therapy by Jill A. Stoddard Ph.D. and Niloofar Afari Ph.D.

The Journal of Contextual Behavioral Science (JCBS) of has articles about metaphors.

• Crego, A; Yela, J.R; Ozores-Pérez, R. (2024). A map of living: Moving through the variations of life with the guidance of metaphors. Journal of Contextual Behavioral Science, 31, 100718.
• Foody, M., Barnes-Holmes, Y., Barnes-Holmes, D., Torneke, N., Luciano, C., Stewart, I., & McEnteggart, C. (2014). RFT for clinical use: The example of metaphor. Journal of Contextual Behavioral Science, 3, 305-313.

If you are interested in learning more about the creation of metaphor from an RFT perspective, check out Ian Stewart's 2001 paper on the subject.