"Dad lends me his credit card."
Translation:아빠가 신용카드를 빌려주세요.
It's not. See the 가? You don't use that when talking to other person directly. Present tense, present interrogative, and imperative have the same conjugation in casual form, the only difference is the intonation. 해요. 해요?. 해요!
Adding 세 originates from adding 시다 to make a verb more polite. Originally it was 하시어, then 하셔, and now it changed to 하세 to ease the pronunciation. Without 시, it would be 빌려줘요.
The sentence could've not use 요 at all, instead using written and formal form, 빌려주신다 and 빌려주십니다.