Mika, thank you so much for sharing your observations. The magnet is actually a poorly drawn claw, and you have to click on asteroids to connect the claw to them. Once you have done this, you can move your mouse to fling your ship around and collide with batteries to collect energy.
The grapple/claw mechanics are a little awkward in the game jam submission, but I'll be releasing an updated version when it is over that should be easier to work with :)