I am using bunpro and reviewing the usage of て＋いる form and I understand it from a technical perspective but I’m having a hard time wrapping my head around using it in examples like this:
電車は東京に行っています
The train is in Tokyo. (The train has gone to Tokyo and is there.)
Why would you use て＋いる form in this way instead of just saying
電車は東京に行きました。
Is this because using just います for 電車 without would be incorrect?
〜ている does more than just describing an ongoing action, it also describes the result of things, which is what happens in that sentence.
電車は東京に行きました could be used to say the train went to Tokyo, implying it may be in Tokyo, but that’s not the information you’re giving, you’re just saying at some point in the past it went to Tokyo.
電車は東京にあります just means there’s a train in Tokyo, but doesn’t say anything else. It could have been put there at some point and never moved from its spot.
電車は東京に行っています however gives all the information that you put between brackets: the train is in Tokyo because it went there and it is there at this moment in time. It describes that the train is in the current state resulting from going to Tokyo, if that makes sense. It’s about describing the current state of the train, rather than something that happened in the past.
For a slightly different example, you could say something like お母さんは怒っている - mom is mad. You could say お母さんは怒る but that means mom gets mad or will get mad. You can say お母さんは怒った but that just means mom got mad at some point and isn’t necessarily still mad now. お母さんは怒っている however is very clear in the fact that mom is mad at this point in time.
You’d want to use あります for trains because いる (and as such います) is about animate objects. But otherwise, it’s not necessarily incorrect, it just carries a different nuance in that it lacks the implication of describing something’s current state.
I have once again confused myself trying to explain grammar (badly) 
@rodan and I have been discussing how to best translate a particular rule in a TCG; the rule goes like this, rough translation included:
自分の場にあるキャラカードが「使用部隊」となっているスキルカードを使い、いずれかのプレイヤーの場にあるスペシャルダブルスカード以外のキャラカードを１枚撰び、捨札置場に置く（使用したスキルカードは捨札置場に置きます）
If you use a Skill Card with a Character Card with a corresponding Unit, select any non-Special Doubles Character Card from any of your opponents and place it in their discard pile. (Then place the used Skill Card in your own discard pile.)
Our particular question is with that beginning part, 自分の場にあるキャラカードが「使用部隊」となっているスキルカードを使い, and even more specifically that となっている. To give some context, Skill Cards can typically only be used by specific Character cards, noted on the Skill Card itself. You choose a Chara card, move it to the battle zone, then use your Skill card.
This rule is from a subset of the normal rules made to be used in quicker matches, so I’m unsure if the となっている is indicating that anything more special goes on in the interaction between Skill and Character. rodan’s best guess so far is that
The issue here is really the verb, not so much いる which always has essentially the same meaning. The thing is that ている describes being in a resultant state. So in an action verb, the resultant state is something that you are “do-ing.” But verbs are broadly active and stative verbs. 歩く is an action, thus 歩いている is “walking”, and you can stop 歩く-ing. And thus are no longer walking.
Something like 送る is a state. Once you have 送る’d something it can not stop being 送る’d. So 送っている is something that is in the state of 送る and thus that is why “sent.” It doesn’t matter whether something has arrived or not for 送る, once you hit the send button it is already 送っている.
There are verbs that make life confusing as they are stative verbs, but states that don’t happen instantaneously, such as 溶ける.
Now all of this will leave you with the question. “Then what is the difference between 送った and 送っている?”
And the answer is ている can only ever be the resultant state, while the past tense of a verb on its own doesn’t always mean that.
Thinking this way is likely to shield you from errors. That much is true. However, from the way the post on Stack Exchange was written, it was pretty clear that his wife mean ‘it’s already been sent’. She fully expected her husband to open his inbox right away instead of continuing to wait. I think we have to deal with the duality of two sorts of ‘current states’ in order to understand 〜ている properly, because there are definitely cases in which it’s meant to express a known current resultant state and not just a subjective observation. Some examples include 知っている, which is the standard (and only correct) way of saying ‘I (currently) know’; 言っていない for ‘I didn’t say that’ i.e. ‘I didn’t say that and still haven’t said that’; and 開いている for ‘to be open (right now)’. These are not the only possible translations of those phrases, but they can be translated that way.
The state expressed by this is just a certain current state. That current state can be an action (e.g. ‘is going’) or a condition (e.g. ‘is waiting’ or ‘has died/is dead’ – the latter should remind you of the meme「お前はもう死んでいる」, which is a classic example). In many cases, both meanings are possible, with context determining what the verb form actually means. However, certain verbs have a strong tendency to be stative or state-changing verbs, and so their 〜ている forms tend to mean ‘has done’. 死ぬ is one of them. ‘To be dying’ is rarely an accurate translation barring half-joking comments like ‘this project is killing me’. 行く and 来る are another two examples. However, when you see something that says「台風が来ています」, let’s just put it like this: if it’s on an announcement, then very logically, it should mean ‘a typhoon is coming’. Otherwise, the announcement is stupid and pointless, especially if it’s written on paper, because there’s no point informing people about a typhoon that has already made landfall. Context determines a lot.
As for how to understand why 〜ている tends to mean ‘to be in a particular current state’, I’d like to suggest that we all remember that いる is fundamentally a verb suggesting active ‘existence in a state’. If you’re not convinced, remember that the slightly more advanced grammar point 〜ていられない means ‘to be unable to continue being/doing ~’. To use a literal (if slightly strange) translation to explain it, you are ‘doing ~ and existing’ in that state. That’s all it means. Remember that the て-form is very flexible and rarely expresses a specific sort of relationship between verbs. As such, all it suggests is a sort of ‘existence in the state of ~’. What sort of existence that is – present perfect or present continuous – is entirely up to context and common usage habits.
Would a native speaker be likely to use something like 溶けているところ to specify “currently in the process of melting” as opposed to meaning “is now melted”?
You certainly could do that. I think it would depend on the context as to whether anything more is even necessary (I’ve never had this conversation in real life).
Also as a side note, I asked my roommate about 送っている and 送った and he understood after I explained it to him, but he preferred 送った for the “sent” usage.
To condense this question a bit:
Would this construction:
X が Y となっている Z
mean “a Z for which X is Y”?
My impression from that thread is yes, but I’m curious if someone can confirm or deny.
I think what’s tripping me up is that the relationship between the modifying verb and the modified noun feels more abstract than I might have expected (if that is what it means).
In the example, by the way, it’s followed by を使い, so if I’m wrong is the alternative:
X が Y となっている Zを使い
X using a Z which is/is becoming Y?
If I’m trying to negate something I am thinking about, do I negate the act of thinking, or would it be best formed another way?
Example;
たくさん雲がある、でも雨が降ろうと思わない。
You negate the thing you’re thinking about, so in this case:
たくさんの雲がある。でも、雨が降らないと思う。
~おうと思う you can only use for actions you will carry out yourself, so I will try to think of an example for that case as well:
ドレスを買おうと思う。 I think I will buy a dress.
ドレスを買わないと思う。I think I won’t buy a dress.
ドレスを買おうと思わない。I don’t think I will buy a dress.
It’s a suble difference in English, but it’s important in Japanese. In most cases the first negation option will be more natural, and fitting, I think.
Okay, that’s what I was wondering, but all I could seem to remember for と思う was that the preceding verb was in the volitional. Your explanation makes perfect sense though, thank you.
That’s the key, how much volition does the rain really have 
.
There’s no requirement for the preceding verb to be volitional with と思う
Yeah, it makes sense that there wouldn’t be now that I think about what is actually happening. I think that was just the only way I had seen the と思う phrase used so far, so instead of pondering the actual construction, I just told myself it had to be preceded by volitional.
is this correct?
私は泳ぐだけと好きです
(I only like to swim)
No, I’m not sure what you wanted to do with と, but the basic pattern for saying “I like [noun]” is [noun]が好き
You can put だけ in between the noun and が to make [noun]だけが好き
However, 泳ぐ is a verb, not a noun, so it needs to be turned into a noun. This can be done by putting こと after it.
So, if we make those changes we get
私は泳ぐことだけが好きです。
There are more natural ways to express this idea, but that’s something you’ll get to the more grammar points you learn.
And just a general note, it’s typically not necessary to say 私は at the beginning of a sentence like this. Unless you state otherwise, people will assume you are talking about yourself.
ohh thank you! I actually put とbecause I thought to express an idea or a thought you put it like (好きと思う) but looks like that logic can’t be used here 
In ～と思う the と is functioning as a quotation particle, but yes, only certain verbs can accept a quotation with them. And 好き is not a verb at all in Japanese, so it’s not in that category for that reason as well.
okay it’s clear now thank you 