It says there is no fear in love, but perfect love casts out fear, because fear has to do with punishment. The passage links mature love with confidence for the day of judgment. See 1 John 4:17–18.
In 1 John 4:17–19 the writer explains how love, when it reaches its intended result among believers, changes their inner posture. It gives confidence rather than anxiety when thinking about the coming day of judgment. Fear is portrayed as linked to the expectation of punishment, so mature love pushes fear away. This paragraph sits in a larger section where the writer circles around a few core tests and assurances: knowing God is shown in lived patterns, especially love for fellow believers, and right confession about Jesus.
These verses connect mature love with confidence rather than dread when thinking about “the day of judgment.” The text’s explicit claim is that love reaching its intended result “with us” produces boldness (verse 17). It also explicitly ties fear to the expectation of punishment, which is why fear and mature love do not fit together (verse 18).
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with 1 John 4:17-18, then read the surrounding section so the answer stays connected to the passage's flow.
17In this love has been made perfect with us, that we may have boldness in the day of judgment, because as he is, even so are we in this world.
18There is no fear in love; but perfect love casts out fear, because fear has punishment. He who fears is not made perfect in love.