Modal verbs are just a group of verbs with a few specific characteristics. They show changes from the infinitive in the first three persons (ich/du/es) and also do not have endings for ich and es.
The plural is always regular, Modal verbs are no exception to this rule. But pay attention to the following translations:

1. können - to be able to
2. müssen - to have to
3. dürfen - to be allowed to
4. wollen - to want
5. sollen - should
6. mögen (used only as "möchte") - (would) like

Modal verbs are irregular not only in form, but also in their use: they can have another verb as a partner. Actually, most of the time, they have another verb as a partner. That verb is then used in its basic form at the very end of that same sentence. See it here:

Ich kann nicht kommen.
I can‘t come.

This peculiarity will not cause you much trouble because, as in English, you have the same phenomenon as you can see in the translation above. So, all you need to do is learn the irregularities in their forms and their meanings and you‘ll be fine. The only thing to keep in mind is the sentence order. The verb in the infinitive is always at the very end of a sentence. This is different from English and many other languages. An example:

Ich kann dich nicht hören. (=hören is at the very end)
I can't hear you. (=hear is not at the very end)

möchten

There is actually no such infinitive as möchten. The origin of this word is mögen > to like. möchten is actually in the so called Konjunktiv II = subjunctive which we will discuss later in this course. Take a look at the conjugation of möchten and mögen:

möchten (=would like)

ich möchte*
du möchtest
es möchte*

wir möchten
ihr möchtet
sie möchten

= The * here and below indicates that this -e- is not the usual personal ending that you know like e.g. in "ich geh.e". There are not personal endings in the 1st and 3rd person of the modal verbs.

mögen (=to like)

ich magx*
du magst
er/es/sie magx*
wir mögen
ihr mögt
sie/Sie mögen

A quick comparison

Ich möchte ein Bier. > I would like a beer (=to drink).
Ich mag Bier. > I like beer (=the taste)

All forms of the modal verbs