The Optative Mood and "Leve"
Modern Swedish does not actively use the subjunctive or optative moods, but you will hear them in fixed, formulaic expressions like wishes, cheers, and toasts. These old verb forms typically end in -e.
At a formal event like a wedding, the most common optative verb you will hear is leve (may [they] live), derived from leva (to live). It is usually paired with länge (long).
"Vare" (May it be)
The optative form of the verb vara (to be) is vare. This form survives today in highly traditional or religious expressions, often to offer blessings (välsignad) or give thanks to God (Gud).
When raising a toast at a formal Swedish banquet, you will often hear calls for ett fyrfaldigt hurra (a fourfold hooray). While everyday birthdays often get three cheers, four cheers are traditionally reserved for formal occasions, weddings, and royalty. It is common to toast to the bridal couple's välgång (prosperity).
"Varde" (Let there become)
The archaic verb varda means "to become." Its optative form, varde, is famously used in the biblical phrase for "let there be" (literally: "may there become"). While old-fashioned, you may hear it used poetically in speeches to bestow a grand wish upon the couple.