The essential Drupal SEO modules are Pathauto, Metatag, Redirect, XML Sitemap, and Simple XML Sitemap. These handle URLs, meta data, redirects, and sitemap generation between them.
Add Schema.org Metatag for structured data to help search engines understand your content better. The RabbitHole module is useful for controlling how taxonomy terms and other entities behave when visited directly.
For more advanced needs, look at SEO Checklist for a guided audit, Real Time SEO for content analysis, and Google Analytics or Matomo for tracking. The Linkit module helps editors build internal links without broken references. Installing all of these gives you a solid SEO foundation, but they are just tools. Ranking well still requires good content, thoughtful keyword strategy, and ongoing optimisation. The modules make implementation easy once you know what you want to do.