Learn French: Il est malade comme toi.

In French, tu is a subject pronoun used when "you" is doing the action (like tu es for "you are"). When "you" comes after a word like comme (like/as) or stands alone without a verb, you have to use the stressed pronoun toi.

Can I use comme to say "I like" something?

No. Comme only translates to "like" when it means "similar to" or "as". To say you "like" a person or thing, you need the verb aimer (for example, J'aime for "I like").

Since Il is masculine, shouldn't we remove the "e" at the end of malade?

French adjectives usually add an "e" for feminine and drop it for masculine. However, if the base dictionary form of the adjective already ends in an "e", it stays exactly the same for both masculine and feminine. So it is Il est malade (he is sick) and Elle est malade (she is sick).

How would I use this to answer a pourquoi (why) question?

If someone asked why he is staying home, you could use this sentence to give the reason by adding parce que (because) to the beginning. You would say: Parce qu'il est malade comme toi (Because he is sick like you). Notice that que shortens to qu' before il because it starts with a vowel.