Five free wordpress plugins every user should use:

Here are Wordpress Plugins Links

For Comment Spaming:
https://wordpress.org/plugins/akismet/

Search Engine Optimization (SEO)
https://wordpress.org/plugins/wordpress-seo/

Contact Forms Related
https://wordpress.org/extend/plugins/contact-form-7/

Social Networking
https://wordpress.org/plugins/ultimate-social-media-icons/screenshots/

Login Security

https://wordpress.org/plugins/login-lockdown/