How to determine bonding and structure of a molecule

This seems like it should be really easy but I've never really understood it for some reason. Is the only way to properly tell what bonding is present by looking at whether the elements are metal and non-metal? I know that non-metals form covalent bonds etc. but I don't know how to figure out what the bonding is from say melting point or something. All I know is ionic compounds are solid at room temperature.
I also don't know how to determine what structure there is and somehow I should know if it is simple or giant or whatever just from looking at the formula.
Would be much appreciated if anyone could help me to understand, thanks.

Before I confuse things, what level are you currently studying at and also what year are you in?

I'm doing a-level in year 12, sorry should have mentioned before

Alright, so yeah, basically the rule of Non-Metal + Non-Metal etc. works - most of the time. Yes, ionic compounds are solid at room temperature but so can covalent, and you have forgotten about metallic. Normally when they talk about properties it will be about conductivity as a solid and in solution as, as a solid, only metal conduct but as a liquid, both metals and ionic compounds conduct due to free delocalized sea of electrons and dissociative state respectively. The questions, at A-Level at least, don't get focus on the type of bonding in the way as suggested up above unless it's obvious like BP difference is low in CO2 in comparison to NaCl. For structures, you'll need to freshen up on VSEPR theory (if you have already learned it, if not, you will!). And for giant structures, I'm not sure if there is a way to learn them, I just rote learnt them ie. the main ones were diamond, graphite, graphene and Sulpher Dioxide.

have a look here and select the section on bonding, it may help a bit
https://www.science-revision.co.uk/A-level_site_index.html

or here if you need to recap work from gcse chemistry https://www.science-revision.co.uk/site_index.html