네 앞에선 심장이 터질 것 같아

The line, explained

You know the feeling: the person you like walks in, and your heart starts pounding so hard you think it might actually explode. This line says exactly that: 'In front of you, I feel like my heart's going to burst.' The key ending is -(으)ㄹ 것 같아. It makes a guess about what is about to happen, and it is also how Koreans describe overwhelming feelings. It is one of the most useful endings in everyday speech.

네 is 'your', and 앞 is front, so 네 앞 is 'in front of you'. Then comes 에선, a squeezed form of 에서는: 에서 means at or in, and 는 adds 'as for' or contrast. So 네 앞에선 is 'when I am in front of you, at least'. The ㅍ of 앞 slides onto the next syllable, giving a-pe-seon. The contrast hints that the singer is fine everywhere else. Just not here.

심장 is the heart as a physical organ, the thing that beats. 마음 is the emotional heart, but when a song wants to say the heart is pounding or bursting, it uses 심장. With the subject marker 이, it becomes 심장이. 터지다 means to burst or explode, used for balloons, fireworks, and laughter: 웃음이 터졌어, I burst out laughing. Here it describes a heart so full it cannot hold any more.

Now the grammar. Take the stem 터지, add -ㄹ, then 것 같아: 터질 것 같아. -ㄹ is a future modifier, 것 means 'thing', and 같다 means to seem or to be like. Literally, 'it seems like the thing that will burst'. After a consonant stem, use -을: 먹을 것 같아, I think I will eat it. The sound 같아 is pronounced ga-ta, because ㅌ moves over to the vowel. Compare -는 것 같아, which guesses about what is going on right now.

Sing it breathless and fast: ne a-pe-seon sim-jang-i, then teo-jil geot ga-ta. Then swap the verb: 멈출 것 같아, it feels like my heart will stop; 녹을 것 같아, it feels like it will melt; 뛰쳐나올 것 같아, it feels like it will jump out; 내려앉을 것 같아, it feels like it will drop. In daily life you will use the same ending for everything from weather to tears: 비가 올 것 같아, 울 것 같아.