Sure. But I would not say it is the first thing you should do.
To prevent your site from getting hacked, start with the following:
- Do not use Admin as your username
- Use a difficult password
- Use two-factor authentication
- Install a security plugin, such as iThemes
- Rename your login page to something else than wp-login.php or admin (use iThemes to do this)
- Backup your site to another server or cloud server on a daily basis
If that’s all done, then your next step would be to buy an SSL certificate.
On the other hand, if you need visitors to send private information over the web to your site, or vice versa, it is very important to encrypt all your data with SSL. A webshop is an example of a situation where I would strongly recommend using SSL.
Another reason to use SSL nowadays is for SEO: Google has announced that websites with SSL will rank better.