Help me understand electrical fields better
You are imagining a 'transmission line'.

Put a switch in series with your voltage source. When you close it, a wave of 5v and some current will progress along the lines at the speed of light (assuming bare wires in a vacuum, slower if there's air or plastic around).

The impedance of the lines is determined by their geometry. The impedance defines how big the current wave is that progresses along with the voltage wave. If the two lines are fairly close together, say 1mm conductors 10mm apart, the impedance will be about 300ohms, something like the old style FM balanced feeder line. If each wire has thin insulation and they're twisted together, then the impedance will be somewhat lower, 50 to 100 ohm range.

What happens when that wave eventually reaches the 100ohm resistor depends on the line impedance. If they're equal, then the current and the voltage waves will be in just the right ratio to be correct for the resistor as well, and the wave will be totally absorbed, leaving a voltage of 5v on the resistor, with the right current through it.

If they don't match, then a smaller wave will be reflected, to take up the portions of the wave that don't match. The wave will continue to bounce between voltage source and load, until eventually the reflection losses attenuate the waves to insignificance, leaving only the DC flowing between source and resistor.