"The beginner is a crocodile."
Translation:La komencanto estas krokodilo.
Only active verbs have objects. The objects are being acted upon, receiving the action of the verb. I throw the ball. Throw is active, "the ball" is the direct object because it is being thrown.
Verbs like "to be" are stative. They express a state of being. What follows a stative verb describes the subject, and therefore is known as a subject complement. He is tall. She looks tired. The cake smells delicious.