Learn Hardcore Spanish (Latin America): La leche está fría en la mesa.

We use está because we are describing a temporary or current condition (the milk is cold at this moment), rather than an inherent or permanent characteristic.

Why is leche feminine in Spanish?

In Spanish, every noun has a designated gender. The word leche is considered feminine, so it takes the feminine article la and any adjectives referring to it must match that gender.

Why do we say fría instead of frío?

Adjectives in Spanish agree with the gender of the noun they describe. Since leche is feminine, the adjective must also be feminine, so we use fría.

What does en la mesa mean in this context?

It means the milk is located on the table. The preposition en can be translated as on, in, or at, depending on the context, but here it clearly indicates the milk is on top of the table.

Can I use sobre la mesa instead of en la mesa?

Yes, you can. Sobre la mesa also means on the table, though en la mesa is very common in everyday speech.