[yetanotherloser]

Not to solder, but to use a crimped connector - the good ones come with hot-glue-lined heat shrink so you crimp the wires for a great connection, then heat the connector and the shrink glues itself down, making a totally sealed connection.

If it's just low volt, low current, low mechanical stress stuff indoors - just twist and solder and wrap a bit of elec tape around it. But if it matters, break out the crimp tool.