Do electric and magnetic fields always form closed loops?

Answer 1

Magnetic fields do, because there's no such thing as an isolated magnetic "pole",

and a magnetic line always starts and ends at opposite poles of the same

magnetized object.

But electric fields don't. You can easily have a bundle of isolated positive charge

over here and a bundle of isolated negative charge over there, whereupon the

lines of the electric field start on one bundle and end on the other bundle.

But electric field lines can also exist in closed loops, and they do that in radio waves, where the electromagnetic field propagates with an electric field component and a magnetic field component, and they both form closed loops.

Answer 2

No, electric and magnetic fields do not always form closed loops. Electric fields start and end on positive and negative charges, while magnetic fields form closed loops around a current-carrying conductor.