I'm not 100% sure, but I got a guess. I suppose because meet with and meet are slightly different?
To meet someone means to be introduced to that person (for the first time) and meet with simply means to accompany someone (regardless of the degree to which the individuals are acquainted).
No, not in this case.
Peter must/has to/needs to meet Julia: पीटर को जूलिया से मिलना है ।
Peter wants to/should/needs to meet Julia: पीटर को जूलिया से मिलना चाहिये ।
Some English expressions can be translated with either construction, but "want" is the part that definitely doesn't overlap.
(Note also that Indian English sometimes makes more of a distinction between the expressions "need to", "have to", "should", and "must" than other dialects, probably because of these two different Hindi idioms.)
OK.. there are a number of rules and formats here .... and I can only use plain English as I am not up on the grammatical terms so much. 1. The form for "have to" is that you always use 'ko' e.g. 'Peter ko' .... and then you use the root of the verb (in this case 'milana' - to meet, followed by simple ending 'hai' etc... So... another example to illustrate this. I MUST eat food now. (or I HAVE to eat food now) would be.... "mujhe abhee khaana khaana hai"... (not that as far as I was taught, mujko and mujhe are interchangeable in many cases) ...does that make sense.? OR 'You have to go to Delhi' is 'Aapako dillee jaana hai" 2. The use of the verb 'milana' to meet has a special rule... You must use 'se' for the person being met . So in this example it is '... Julia se milana.... ' Another example but forgetting point 1 for now might be.. 'I will meet my grandfather' which would be (using this rule) 'Mei apne dada se milunga' (where apna is used because it is MY grandfather and that's another form in Hindi also'). Or 'I am going to meet Peter' is 'main peetar se milane ja raha hoon' ( मैं पीटर से मिलने जा रहा हूं). I hope this answers what you were asking about. :)
"A modal verb is a type of verb that is used to indicate modality – that is: likelihood, ability, permission, request, capacity, suggestions, order, obligation, or advice. Modal verbs always accompany the base (infinitive) form of another verb having semantic content."- Wikipedia