melt (away) into something
phrasal verb with melt verb uk/melt/ us/melt/
融入…中
to look so similar to something else all around you, or to be so much a part of it, that people do not see or notice you
The security men just melted into the background until they were needed. 保安人员都躲在不显眼的地方，直到需要他们的时候才会现身。