。
Will you marry me?
Literal
I [with-と] marry-[for-me-か].
結婚する ('to marry') takes と for the person married. The pattern [verb]+てくれます+か asks the listener to do the action for the speaker's benefit — here making it a proposal. The question particle か is retained (unlike fully casual dropping) because this is a polite consequential question. The archetypal marriage proposal in Japanese.