Learn Swedish: Länge leve bruden och brudgummen! - Long live the bride and the bridegroom!

This is the optative mood, sometimes called the present subjunctive. It is an old verb form used to express a strong wish or hope, translating to 'may they live' or 'long live'. In modern Swedish, you will mostly encounter it in fixed, formulaic expressions like this one. It is usually formed by adding -e to the verb stem.

Why is the verb placed before the subject (leve bruden rather than bruden leve)?

This is the standard V2 (verb-second) rule in action. Because the sentence starts with the adverb länge (long), the verb leve must take the second position in the clause, pushing the subjects (bruden och brudgummen) further back.

Why does brudgum (bridegroom) get a double 'm' in its definite form brudgummen?

In Swedish, a final consonant is often doubled when adding a suffix to preserve a short vowel sound. Even though the main stress is on the first syllable (brud-), the 'u' in -gum is short. To keep that 'u' short when adding the definite suffix -en, the 'm' must be doubled.

Can I use the phrase länge leve... outside of formal toasts?