Hi.
For uses other than a simple test, I like the connection to be more solid than just twisted together.
Just like the other posters have said, the connection won't stay very good very long.
If You don't want to solder the connections for some reason, at least use some screw-on or crimped connectors to secure the connection. There's plenty of options out there in the hardware stores el. department, better ones at RS.
On the tools section there's also cheap pencil type soldering irons and rosin core solder, do take a look at those as well while You're there

.
Just my 0.02€
Sam