"A father is a man."
Translation:Папа — это мужчина.
That's not true, actually. "Есть" is the infinitive "to eat", but it's also the present tense form of "быть" - to be, so it actually can be translated as "is" sometimes. Javi is trying to use "есть" in this meaning. It doesn't work just because that isn't how Russian works, I can't really explain why.
Father eats men would be "папа есть мужчин".
It's not incorrect, but it would sound awkward. "Быть"(to be) nowadays is usually omitted in the present tense.
Она была здесь.(She was here) Она здесь.(She is here) Она будет здесь.(She will be here)
Карандаш здесь.(The pencil is here) Здесь есть карандаш.(There is a pencil here)
It could be used in formal speech, in some cases when omission would change the meaning of the sentence, to spice up informal speech(not randomly, you have to know if it works).