I have a simple but confusing answer...
Mass is charge. Inertia is the resistance to leaving the influence of one set of fields and the inverse being the "willingness" to enter another due to mutual attraction/repulsion due to Like and unlike forces...
All things that have mass (even some that don't) have Charge. So perhaps a better refinement is this: Mass is Energy, Energy is defined as Equal Electric Field at a 90*angle to Equal Magnetic field in Harmonic Ocsillation. Therefore by proxy Energy is dual-charge (Electric Charge & Magnetic Charge).
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