Sometimes fluids are slow-moving enough that it takes timelapse techniques to reveal the flow.

 

Being silly putty, it’s a non-Newtonian fluid, meaning that it has a nonlinear response to deformation.

 

With a strong enough magnet, the putty makes for an impressively tenacious creeping flow.

 

The magnet’s field exerts a force on the iron-containing putty, which, because it is a fluid, cannot resist deformation under a force.

 

As a result, the putty will flow around the magnet, eventually coming to a stop once it reaches equilibrium, with its iron equally distributed around the magnet.

 

Assuming the putty is homogeneously ferrous (i.e. the iron is mixed equally in the putty), that means the putty will stop moving when the magnet is at its center of mass.