"My son is intelligent."
Translation:Mi hijo es inteligente.
Typically "es" denotes permanence or continued quality vs. "está" is temporary or the current state. For example, "eres muy hermosa" and "estás muy hermosa" both means "you are very pretty" but the latter can be construed to actually "estás muy hermosa (hoy/ahora)". This means that if someone "estar" the quality you're describing it means it's a temporary shift from the norm.
Es comes from the root ser (weird, I know), which is like an intrinsic characteristic. Esta comes from the root estar, which is more like a state of being. If I say "I am happy", I would use estoy (from the root estar). If I say "I am a happy person", meaning it's part of my character, it's soy (from the root ser)