There is no way to make a form require a company name. Say, it's a sponsorship form and those sponsors are companies, it's too easy for the person filling the form to skip the checkbox for organization and not input the organization name.

You should be able to make a form for "organizations only" and then instead of "first name, Last name," it requires "company name." Now, you'd still want the name fields for the org contact, but that person should not become a registrant.