The phrase "melting into" refers to the process of slowly blending in or becoming one with something. There are several synonyms that can be used to describe this phenomenon, such as merging, fusing, integrating and blending. The word "merging" suggests a gradual joining or the coming together of two entities. On the other hand, "fusing" is used to describe a more complete integration or the becoming of one whole. "Integrating" also implies a complete merging of two or more things. Lastly, "blending" refers to a smooth and seamless combination of elements. All of these synonyms are useful in describing the process of melting into something.