verb conjugation:

https://www.grammarly.com/blog/linking-verbs/'

From that linked article: "In subject-verb agreement, linking verbs match the subject.

When it comes to subject-verb agreement, the linking verb still matches the subject. This remains true even if the subject is singular and the predicate nominative is plural or vice versa.

The weirdest animal is giraffes.
Giraffes are the weirdest animal.

If the sentence still sounds awkward, even though it’s grammatically correct, you can always rephrase it.

The weirdest animal is the giraffe."