Amyotrophic lateral sclerosis (ALS) represents the major adult-onset motor neuron disease. Analyses of ALS animal models have shown that motor neuron death starts with neuromuscular junction (NMJ) destruction and distal axonal degeneration. Most importantly, motor neuron death results from pathological events occurring outside the motor neuron, especially in glial cells and skeletal muscle and, surprisingly, is associated with pathological defects outside the motor system. In particular, ALS pathogenesis includes systemic defects such as muscle hypermetabolism, energy deficit, and widespread alterations of lipid metabolism that were shown to participate in motor neuron degeneration. Current research should now focus on understanding the relationships between these pathological hallmarks and how such global defects lead to the ALS-linked selective loss of motor neurons.