How to set a gradient background to a Material Button?

LE: From my point of view I suggest you use Button or AppCompatButton.

Try this:

gradient.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <gradient
        android:angle="0"
        android:endColor="#027FEE"
        android:startColor="#2CC6F2" />
</shape>

button.xml

<!-- replace MaterialButton with Button or AppCompatButton -->
<com.google.android.material.button.MaterialButton
    android:id="@+id/materialButton"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@drawable/gradient"
    android:text="Hello" />

Result:

With corner radius change gradient.xml to:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <gradient
        android:angle="0"
        android:endColor="#027FEE"
        android:startColor="#2CC6F2" />
    <corners android:radius="32dp"/>
</shape>

Result:

To use a custom drawable background with the MaterialButton you can use the android:background attribute:

<MaterialButton
    app:backgroundTint="@null"
    android:background="@drawable/bkg_button_gradient"
    ... />

NOTE: It requires at least the version 1.2.0-alpha06

Currently it is very important to add app:backgroundTint="@null" to avoid that the custom background doesn't get tinted by default with the backgroundTint color.

With lower versions of the Material Components Library you have to use an AppCompatButton.