An example of metaphor in popular science writing:
"Lithium is a bewitching element and, when in the form of lithium chloride powder, absorbs moisture from the air and melts before your eyes."
de Moore, G., & Westmore, A. (2016). Finding Sanity. John Cade, lithium and the taming of bipolar disorder. Allen & Unwin.
LiCl is deliquescent. That means it is not just hygroscopic (i.e., able to absorb water from the atmosphere) but absorbs sufficient water to dissolve and form a solution.
Melting is quite different from dissolving as it produces a pure liquid not a mixture (solution). Lithium chloride melts at 605˚C: considerably above room temperature
Learners may not appreciate that melting and dissolving are quite distinct (as the difference is more obvious from a theoretical description than from what may be observed, e.g., an ice cube in a glass of water versus a sugar cube in a glass of water). For example, a learner may suggest that sugar melts when placed in water.
However, in everyday language things are said to 'melt away' with a much wider range of application than actual melting. I am assuming the authors here are using 'melt' in a metaphorical sense and do not hold the misconception that the solid anhydrous LiCl actually melts.
