The Direct Object may be:-

1. A Noun.

Lightning struck the temple.

2. A Pronoun.

Warn him.

3. An Adjective (used as a noun).

We must help the poor.

4. A Verbal Noun (or Gerund).

He practises wrestling.

5. An Infinitive.

I am learning to row.

6. A Phrase.

The agent promised to put things right.