Is it suitable?

I am just a newbie with farming.
I've decided to plant fruit trees at first.  
I have been thinking about the selection of tools .
The situation is that I have one metal detector shovel  to do metal detecting. 
it's just like this one.
Is it suitable for planting trees?
maybe my question seems weird.

It looks like a trenching tool . Yup it digs holes so yes you could use it to plant trees if you wish .

It looks like it's foldable. You might want to get another shovel for at home use before that one is ruined. Get a good quality tool while you can. Mail order is your best bet.

Mail order is a good alternative if you don't have good local nurseries. My only experience is with the Austin area, which has not only a large percentage of active gardeners, but a large percentage of organic gardeners as well. That supports a lot of small local nurseries (more than one that is solely organic) and most of these carry at least one line of high quality tools. Especially as you're just starting out, it may help you to handle the tools to get an idea of how the different weights and handle lengths will work for you.

Even if you go mail order, I would still suggest that you at least go into a big box store and handle some of the tools. Different people have different preferences. As an example, my family has two high quality garden forks that together cost nearly 200 dollars. My mother and I have a high difference of less than 4 inches, but I greatly (mine was the most expensive) prefer a longer handle length so that when I step on the tool I don't have to bend over to control it. My mother prefers a shorter handle that you lean your body weight on and hardly every needs to step up on it. Both of these are great tools but because we have different styles of using them we each needed our own fork.

As for a tool to plant trees, trenching shovels are wonderful. They are narrower which makes it easier to punch deep into heavy soils. For larger digging projects they might not be the best because the don't move a huge volume at a time, but definitely enough for a hole. But a full sized trenching shovel is much longer than a folding model.

Every garden is different in what it requires. In mine, if I absolutely had to, I could get by with a shovel, pruning shears and a decent set of gloves. Instead I have a good quality garden cart, three different styles of shovels (including a trenching shovel), a pick ax, two gardening forks, a popup weeder, pruning shears, bypass lopers and a basic hoe. Everything but the hoe gets regular use. This collection of tools has built up over time as I've expanded the gardens.